Terminator is the border between day and night sides of the planet, also known as a "twilight zone". It's also the name of a franchise based on a type of robots employed by Skynet for its noble goal of cleaning Earth of human scum (initially humanoid infiltrator type, but later all Skynet robots came to be called that). But of course you came here because of Space Marines in Terminator armour...
Terminators are Space Marine or Adeptus Custodes veterans who have managed to earn the right to wear Terminator armor through exemplary service. Terminator armor or "Tactical Dreadnought Armor" is a holy relic of a Space Marine Chapter, often dating back to the years of the Horus Heresy and so they are revered as holy relics and a physical manifest of the chapter's undying fighting spirit. Because most chapters generally have far fewer Terminator suits than standard power armor suits, Terminator armor is generally reserved for the veterans of a Chapter's first company (though codex-deviant chapters will have their own rules on who gets termie armor). In spite of their incredible rarity, Terminators are frequently deployed to Space Hulks since it's the only level of protection that can withstand the intense radiation found within many hulks.
As the Imperium is the Imperium, new suits of Terminator armor are produced very slowly these days by Forge Worlds due to their high cost and the fact that the Adeptus Mechanicus continues to go on its Alzheimer's streak by constantly forgetting how to make anything good besides Titans. Instead, most Terminator armor is now made from existing Terminator suits, refurbished for battle, likely with only the occasional new part produced when needed.
Because of the Terminator armor's sheer weight and bulk, they're slow-moving and will likely be shot at if foot-slogged across the field, which isn't really a problem until someone whips out the Lascannon, Plasma Cannon, and all other forms of dedicated anti-armor weapons. So termies get around by deep striking with Teleporters or riding Land Raiders, which are the only transports capable of supporting Terminators (besides the fliers -- Thunderhawks, Storm Eagles, and Stormravens).
The original pattern, developed during the Great Crusade based on fusion-reactor maintenance suits, is the Cataphractii pattern. It had roman-like, slab-like pauldrons (which apparently held shield generators), which enabled greater protection at the cost of preventing the wearer from moving with any sort of speed. In crunch terms, this translates to a higher invulnerable save than the Indominus/Tartaros armor at the expense of gaining the Slow and Purposeful rule.
A later development, sacrificing a little protection for increased mobility, was the Indomitus pattern. This is the most commonly produced pattern, as Cataphractii armour was said to be in declining use due to its limitations and Tartaros armour was resource intensive, placing Indomitus in a comfortable medium. It has the familiar hunchbacked-bulldog/horse appearance, as seen in the majority of Games Workshop Terminator kits (although they now produce plastic kits for the other major patterns too).
Though inferior to the Cataphractii pattern in protection, and inferior to Tartaros pattern in mobility, the indomitus pattern has quite advanced auto sense systems that are unavailable in normal suits of power armour, and have not been entirely made evident from portrayals of the other types. These senses allow the user to track unseen targets and to know the precise location and condition of their squadmates at all times, while this is evident in the video games as a passive mechanic it can't really come up on the tabletop since the player sees everything anyway (except for "blips" in Space Hulk) But these systems are noted in the RPG and various novels such as Master of Sanctity where the new user has to get used to a whole new suite of tactical information on top of actually learning how just to walk in the armour itself (hint: it's difficult).
The most advanced pattern, using systems developed for the Mark IV "Maximus"-pattern powered armor. Tartaros Armor delivers the same level of protection as the Indomitus pattern but is much more mobile, with sensibly-sized pauldrons and an upright stance. Due to the advances in Pauldron Technology, Terminator Squads in Tartaros Armor can Sweeping Advance, unlike the others encased lesser models.
There are other patterns mentioned in the fluff but not yet seen on the tabletop, or available elsewhere in such small numbers they can be counted as unique variants.
The Saturnine pattern has only been given a passing mention in Forge World's Horus Heresy rulebooks, where it was mentioned as being similar to the Indomitus and Tartaros patterns in function (if not design). However, some people have speculated that it is a revamp of an old Rogue Trader-era version of Terminator armor, as such a suit was recently shown in interior illustrations for the novella Meduson. From the pictures, this pattern looks like it is intended as a heavy fire platform, like a less Xzibit-friendly version of 40K-era Centurion Devastators. Which is awesome. However, this specialisation, and the fact that the armour was described as a custom job devised by Vulkan rather than a general-issue design, goes against it being the Saturnine pattern.
The Iron Hands also developed their own variant on the Indomitus armour, called the Gorgon Pattern. This armour was bonded to its wearer in a painful cybernetic connection, so he could never remove it, but also meant he was even more resistant to injury, and it had a unique field effect that caused blinding bright flashes whenever it was struck. This pattern is nowhere to be found after the Heresy, likely because Ferrus Manus didn't live long enough to work out the kinks in the design.
The Minotaurs have widespread access to a rare type of Terminator armour, known as the Arkonak Pattern. However, every official illustration of a Minotaurs Terminator to date has them wearing either Indomitus or Tartaros armour, including their Chapter Master (the original Tartaros Terminator model).
There are some rare versions of Terminator armor that can be used by ordinary humans, but access to these is restricted to a select few members of the Inquisition; even then, they aren't quite as potent as the versions used by Space Marines, due to lacking a Black Carapace.
Adeptus Custodes have Aquilon Terminators. Their armour was referred to as Cataphractii pattern in the short story Hands of the Emperor, as expected its has rules different from (read: better than) the Space Marine version. Much like Tartaros it can fire Overwatch and make Sweeping Advances. Aquilons have better weapons and equipment than what Astartes of both flavors get.
Terminators are usually equipped with a Storm Bolter in one hand for ranged combat, and a power fist, chain fist, or power weapon in the other for close combat. The Storm Bolter can be switched for a Heavy Flamer or an Assault Cannon. For extra zip, a shoulder mounted Cyclone Missile Launcher (basically a portable manticore) can be purchased and equipped. Assault Terminators are tooled to close combat with all manner of deadly shit such as Lightning Claws or a Thunder Hammer and Storm Shield.
Either way, a shooty or choppy termie won't disappoint if used properly.
Chaos Space Marines have a different setup for weaponry. Chaos Terminators do not distinguish between long and close range combat and equip both types of weapons, though in place of an assault cannon they use the Reaper Autocannon. Lacking loyalist-exclusive weapons, they rely on Marks of Chaos for added power.
During the Great Crusade and Horus Heresy, Terminators could also use combi-weapons, Plasma Blasters, Volkite weaponry, and Multi-Meltas, depending on the Legion they came from.
Moar Mechanicus Fail
Originally, as in Great Crusade originally, the Mechanicus could actually make Terminator armor. It was called Cataphractii-pattern armor (though there were many patterns of terminator armor at that time) and it was MADE of WIN. It had the freakiest pauldrons ever, but was pretty much unbreakable. Wait, you thought that Terminator armor got its toughness from it being STRONG? Of course not, it's from the Marine itself!, the only protection the armor provides is the +2 armor save and 4++ invulnerable save. After the Horus Heresy, the Mechanicus forgot how to make the good armor, so they decided to test whether or not the Emperor's armor would blend. It did, so they took all of the tiny fragments, and stuck one piece in the shoulder of each new suit of Terminator armor, underneath the fancy Crux Terminatus. Never mind how this still works for all those Chaos Terminators, but we suspect that it's just to troll the loyalist terminators.
So all of the new, fancy-looking armor you see today is actually crappier than the goofy old armor. That's mostly how stuff works in 40K, technology actually gets worse as time moves on so we won't be surprised if by 51st millennium, everything reverts back/progresses to Warhammer Fantasy Battle. Considering the apocalyptic devastation happening on every battle field to every faction...that actually is plausible-hey wait a minute! Does this mean 40K might actually be a prequel to Fantasy Battle!? It all makes sense! The last battlefield (world) in the galaxy (probably last freakin' planet in the galaxy by then)... And then, Age of Sigmar.
Oh, and the Mechanicus has not forgotten. The Grey Knights actually gets new powered and terminator armor to replace losses freshly made for the individual Astartes by the Mechanicus. Having your own personal forgeworld does have its advantages.
(Sigh...) Rant aside, Terminator armor is still in limited production in 41st millennium. While not as protective as the original Cataphractii armor it is more maneuverable and thus inherently more practical. The suits are effectively hand made by a team of master-skilled artisans who would regard any defects or mistakes in their product as a inexcusable blasphemy. The end result is an armor that is the standard-to-which-all-others-are-judged in terms of personal protection that can and will last millennia on nightmarish battlefields while toting weapon systems (if oddly few) that can fuck up main battle tanks. But it takes that single team of artisans years at a minimum to make a single complete suit. Is it worth it? Some Space Marine Chapters say no, but most say yes. You decide.
Also, for some reason, there are no Terminator suits designed specifically for hefting extremely heavy weaponry around. Except you know Centurions. If only they had some weapon combinations outside the gravitron load-out that were actually practical.
As of 5th edition, Storm Shields were given a 3+ invulnerable save against EVERYTHING (including yo momma) to ensure that players started using Storm Shield + hammer terminators (and possibly to increase GW's profit margins, who knows?). This of course has lead a number of players to vent their rage at the new cheddar-infused protection that termies have been given. Combined with the 2+ save they already get, assault terminators are arguably the most resilient squad in the game, and are nigh unkillable by several high-powered weapons including:
- weapons that are used to tear apart planets
- turrets specifically used to destroy titans and spaceships
- The first few searches retrieved after entering "Client/Server database" into Google (June 2013)
Marine players can of course take 3 10-man squads of these things, and whilst each dude costs 45 points each, their inability to die even to Nurgle fondling them whilst teleporting right next to the enemy army would make most players prefer to flip the gaming table over and claim insanity, in the aim of destroying as many of the blighters as possible. Mind you, Wraithblades ain't much less overpowered
(umm 3+ save and 4++ save is not nearly as bad...) They're T6 motherfucker. Good luck wounding them.
Actually, Terminators are not very tough at all considering their cost. You can kill Assault Termies easier with sharp sticks or lasguns than with lascannons point for point though, so don't bother wasting your anti-heavy on them and just pound them with anti infantry.
In video games
Likely due to the fact that Relic couldn't figure out how to balance Chaos Terminators, the Dawn of War video games only see loyalists use them (outside of the Chaos Lord in DoW II), in which they serve as very powerful late game infantry, though they lose in combat against Meganobz, Pariahs, and the Seer Council. They also get minced by Banshees, who not only out-DPS them when fully upgraded but can also break their morale in seconds....
Regular Terminators in DoW II are armed with storm bolters and one of them can take a Heavy Flamer, Assault Cannon, or Cyclone Missile Launcher. They're invaluable for supporting your troops of any kind with their variety of weapons and can hold their own in an assault that doesn't involve dedicated heavy melee units thanks to their power fists and toughness. They aren't built like normal units and are instead called down by a global ability, but only a Force Commander has access to the Assault Terminators
Assault Terminators in Dawn of War II are virtually unstoppable in melee and can only be beaten by sheer numbers. Their starting Storm Shields and Thunder Hammers give them more health than normal terminators, but it's best to trade that off for Lightning Claws. At the cost of bringing them down to normal terminator health, reducing their effectiveness against vehicles, and removing their ability to stun vehicles, they get added melee damage against infantry and area of effect attack, so anything that gets into melee with them that isn't a vehicle is going to die. Being just as tough as normal terminators still makes them a nightmare to kill. Trying to bring down LC Assault Terminators without using heavies like predator tanks and Carnifexi is a hell of a challenge.
They were so strong that later patches took away their ability to level up as they killed units, because at level one they were already packing killing power comparable to a maxed level Nob squad. This is on top of being teleported rather than built at a base and having the ability to teleport to retreat or get in close to melee (normal terminators can do that but it's more dangerous coming from a melee squad). Three space marine players dropping three assault terminator squads in someone's face is widely considered to be a form of griefing.
Fortunately Focus Home Interactive decided to take their time to invest in a game with an actually canonical portrayal of Terminators. (Shame the game was released unfinished, just like nearly every big-budget, AAA title nowadays. UPDATE: fortunately the game has been patched and new features added.)
On the Tabletop
Despite their portrayal in the Codex fluff and Dark Library books as unstoppable juggernauts. Codex: Space Marine Terminators leave less tactically inclined players more disappointed than a senior on prom night. Their legendary durability are now surpassed by much uglier Centurions. Assault Terminators require TH/SS combos to reach damage parity with much newer and more useful miniatures. Ten model units of properly kitted out Sternguards or Devastators can dish out more ranged damage than a Terminator squad with two Assault Cannons or Cyclone Missile Launchers. The best way to arm "shooty" Terminators is to give them Chainfists to deal with vehicles.
Terminators frequently require Land Raiders, flyers or teleport homers to get them to where they need to be. It's not all doom and gloom, but getting the most out of Terminators requires a little more forethought and cash than any casual player would be willing to invest. Otherwise, they windup as little more than very expensive Distraction Carnifexes.
Deathwing Knights are considered to be one of the best Assault TEQs in the game. While "regular" Deathwing allow two Plasma Cannons for every ten models. Deathwing Command and Paladin squads can upgrade one model to an Apothecary for "Feel no Pain". The best shooty Terminators are arguably Grey Knights with the option to take Psilencers, Deathwing with Foe-smitter and a Land Raider Crusader or Deathwatch Termis armed with either five Assault Cannons and/or Cyclone Missile Launchers. Grey Knights are also one of few ways players can take Terminators as troops. Unlike Paladins however, they can't take Storm Shields. Shooty Deathwing or Grey Knights will need an HQ with the appropriate weapon and the aforementioned Land Raider to get over thirty shots during the shooting phase. You won't missing those two Terminators when you have twin Assault Cannons and six Hurricane Bolters. Not to forget Frag Assault Cannons to help up with Overwatch. Since Psilencers are special weapons weapons for Termi HQs. Grey Knights can this pull off without a relic. The only way to get more Terminator dakka than this is playing Horus Heresy and taking Fulmentarus or Tyrant Siege Terminators with a Spartan as their dedicated transport.
Deathwatch Terminators also have the option of buying Melta Fists. You read that correctly. These are Power Fists with Melta Guns mounted on them to melt MEQs, TEQs and Monstrous Creatures. Any survivors have to deal with five Powerfists or a painful round of overwatch. The only real downside to Deathwatch Termis is that they have no options for Dedicated Transports of any kind and are limited to five models each. You could upgrade them to have both Heavy Thunder Hammers and Cyclone Missile Launchers. However doing so is generally considered a huge waste of points.
The other option worth considering is to crack open that wolf codex (sigh) and run wolf-guard terminators. Each Wolfy-woof terminator comes at 33pts base and may take ANY item form the terminator weapons list. Kit them out like sternguard by giving them a combi weapon and power weapon or (free) stormshield. Vola, you have a 2+/3++ combi wielding unit with deepstrike for only 1-8pts more (per model) than a equally kitted sternguard group. Or give them meltaguns, shields, and chainfists for the most terrifying tank-killing depstrikers you'll ever see.
Finally, for some strange (or insane) reason if a player is still committed to fielding Terminators from Codex: Space Marines. Forge World has them covered with Tyberos the Red Wake. He comes with two Lightning Claw Chainfists and has one of the best models in the game. His rules allow him to make one unit of LC equipped Terminators as Troops. This is invalided if they are upgraded to TH/SS combos. The real purpose of this strategy is that it allows a player to field a Land Raider with "Objective Secured". Something only Grey Knights Termi and Black Templar Crusader Squads are able to pull off.
New Codexices are forthcoming. So information is scarce. What do know is that the Terminator have been buffed with two wounds, Teleport Homers allow Terminators to move 6" within the Homer. Along with improvements for Power Weapons across the board. Power Fists, Chainfists and Thunder Hammers are no longer Unwieldy. Power fists have -1 one on hit roles, Chainfists are AP -4 with fixed damage. Thunder Hammers are improved Power Fists with more reliable damage. While the Assault Cannon has been nerfed to being only useful against blob armies. Cyclone Missile launchers are now the go to choice for Dakkanators. Twin Linked has been changed so that these weapons can fire twice. Making the Land Raider Crusader a decent choice for taking on all comers if upgraded with a Multi-Melta. Take a Termi-Captain and keep him within 6" so you can re-reroll 1's. So nothing can escape their reach. This excludes any possible Relic shenanigans.
Dark Angels, Space Furries and Blood Angels still can't take Cataphractii or Tartaros Termi-armor outside of 30k. Despite the fact that these guys are more tech savvy and know how to take care of their shit better than other chapters with the exception of the Raven Guard, Iron Hands and the Salamanders. So fans will have to cross their fingers and hope GW comes to their senses.