"IT IS THE BEEEEEINNNBLEEEEHHDDDEEEE!" ~ Captain Diomedes of the Blood Ravens.
The Baneblade is a big fucking Imperial tank Warhammer 40,000 universe, known generally for an impressive arsenal (OF GUNS), and disappearing en masse. Besides looking totally kickass, it stomps a lot of ass too. It is supposedly one of the oldest and largest tank designs used by the Imperium, despite that it's actually medium-sized according to the old Epic fluff. Then again, the "big" tanks in Epic were closer to moving, gun-mounting cathedrals. This is an actual tank. A manly tank. The manly tank. If only the Mechanicus had looked at the Battle Cannon, looked at the Baneblade, and scaled-down the Baneblade design and slapped on single-barrel heavy weapons instead of twin-linked and a long-barreled Battle Cannon. But no, they had to use the freaking tractor STC...
The Baneblade first appeared in the Space Marine edition of Epic, where it was the Imperial Guard's standard super-heavy tank (it says a lot about the universe that there's such a thing as a "standard" one). This version was armed with a turret-mounted Battle Cannon (with the same stats as the one on the Leman Russ Battle Tank, despite the turret being the size of a Leman Russ), two Lascannons, and a bunch of dice worth of "Bolters" to deal with swarms. Despite obviously having a big gun on the lower hull, there was no representation of it in the tank's rules. Fluff described the hull as the size of a city block.
Being a standard version, there were variants at that point, and only three:
- The Stormhammer was effectively a moving fortress, and the precise armament is hard to say given the odd way the game treated "Bolters;" anything from an officer's Bolt Pistols to both a Leman Russ' Heavy Bolters was one attack dice with the same stats. This means this particular monster might have up to 24 Heavy Bolters in addition to two turrets with two battle cannons each. Basically, you park it in a place and then forget about that place, since it is now Defended.
- The Shadowsword was one of two Titan-killing variants, armed with two Lascannons and some "Bolters" like the Baneblade, but with the rear hull built up into a giant casemate mounting a fixed Volcano Cannon, a giant laser weapon normally mounted on Titans.
- The Stormblade was a second variant of the fixed-weapon hull, and proof of how incredibly fucking HUGE the old Epic fluff made the Baneblade chassis; no fruity Lascannons for this one, the sponson weapons were a rack of missiles and a fucking Battle Cannon. Your main gun was a Titan-grade Plasma Blastgun with a Hellion anti-Titan missile slung on the top. Potential drivers had to produce written proof that they were bad enough dudes to save the President before they'd even be considered. Forge World makes a Stormblade, but it just sits there (eating an entire sack of dicks) because it knows it will never be cool enough to have a sponson-mounted Battle Cannon.
The Chaos legions have their own version called the Decimator, which is, in fact, an early pre-production model super-heavy tank that would later lead to the development of the Baneblade. It has replaced its bolters with lots and lots of Reaper Autocannons, resulting in it being far nastier against medium armor, though its main cannon is not turreted, meaning the entire tank has to turn to fire it.
Here are a few fun facts about the mighty Baneblade:
- When the Adeptus Mechanicus discovered a STC printout with the designs for a Dark Age of Technology tank, the design was classified as a 'light battle tank.' Citation Needed In other words, the super heavy moving fortress of rape and death that we know as the Baneblade was originally considered the equivalent of a Leman Russ Battle Tank and that there might be an STC for an even more powerful tank lying around somewhere.
- At the time of the Great Crusade, there used to be entire
companies battalions of Baneblades (it was described as being the "mainstay" of the Imperial Army). Nowadays, regiments with anywhere near a hundred Baneblades are virtually unheard of, and any Imperial Guard force can count itself lucky to have just one in their possession. If a Baneblade gets lost in combat, chances are that the Mechanicus will throw a bitchfit and pull out all stops to recover the hulk. This was the case seven years before the Third Armageddon War, when an entire Imperial Guard Army Group (100,000+ guardsmen) was deployed to Golgotha to retrieve Yarrick's Fortress of Arrogance and a bit of STC teleporter tech.
- Production of Baneblades continues to the 41st Millennium. Although the STC has been shared with a select few of the countless forgeworlds in the Imperium, the majority of Baneblades still come from Martian forges. As a result, the Macharius Heavy Tank was re-discovered/developed explicitly for armored regiments that needed something meaner than a Leman Russ Battle Tank but needed scientific notation to denote their place on the Baneblade delivery list.
When people say that the Imperium is now but a shadow of humanity's past glory, they ain't kiddin'.
 Warhammer 40,000
Scratch-built Baneblade models with homebrew (read: unfair) rules have been kicking around since roughly ten minutes after it was introduced in Epic, but it wasn't until Forge World was founded that Games Workshop ever considered releasing an official model. The Baneblade then became available as a plastic kit from GW itself, along with a six-option kit for the casemate fixed-hull variants. With the sixth edition re-release of Apocalypse, GW redid the kit again to make all eight of their official variants (everything in the list below except for the Fellblade, Plaguereaper, Stormblade, and Stormhammer).
There are currently ten official variants (nine of which have models), with the names being a nightmarish jumble of "Bane," "Sword," "Storm," "Shadow," "Blade" and "Hammer" to the point it's difficult remembering which is which.
The modern Baneblade mounts what's known as a "Baneblade Cannon" (representing belated recognition that the thing in the turret is really huge and so probably not a Battle Cannon) with a coaxial Autocannon, the same two Lascannons it always had, two Twin-linked Heavy Bolters in each sponson and another two on the hull front, and a Demolisher Cannon where the Mysterious Not-A-Weapon was once mounted. This leads to the well-known ELEVEN BARRELS OF HELL, though the vehicle has options for two more sponsons to be mounted (each with another Lascannon and Twin-linked Heavy Bolter) which raises the bar to seventeen. This option can only be taken on the GW plastic kit, as the old Forge World models were shorter, sillier-looking, and had no place for them. These were given their own pattern in the fluff, and thrust upon an unsuspecting Forge World (the other kind) to make and produce for all eternity.
The Baneblade is so awesome Commissar Yarrick uses a customized, "commandeered" Baneblade as his own transport. It's known as THE FORTRESS OF ARROGANCE and it makes Heretics and Xenos wet themselves. Although Yarrick did leave the thing parked on a world of Orks by "accident".
The Banehammer fields the Tremor Cannon in a forward-set casement, a weapon that can turn a huge segment of the battlefield into a patch of flying rubble, slowing down the enemy long enough for the rest of the army to destroy them. It can also carry 25 soldiers, and has enough room in the rear deck to let ten of them stand outside and fire.
The Banesword is a siege tank: its Quake Cannon can be fired as a barrage weapon at a massive range to destroy up to 15' away, use this to troll the WFB players on the next table.
The Doomhammer is a tank-killer. With a modest 5" blast but stats befitting a tank hunter, the Magma Cannon can reduce all but the largest of titans to scrap. It can also carry 25 soldiers, and has enough room in the rear deck to let ten of them stand outside and fire.
The Fellblade is the Space Marines' main super-heavy tank, not used very much since the Horus Heresy. It's not so much a variant of the Baneblade as a sibling tank, with a unique Forge World kit to make it. Like pretty much everything else the Space Marines have, it is superior to the Imperial Guard's equivalent.
The Hellhammer has the same profile as the Baneblade -- it doesn't have a big armored casement like the others, but rather the same comically-small pivoting turret. It uses the Hellhammer Cannon, which is shorter, but no less deadly than the Baneblade Cannon, and strikes harder but on a smaller area, giving exactly zero fucks about the cover in between.
The Plaguereaper is a Baneblade variant exclusive to the forces of Nurgle. It's a corrupted baneblade chassis with its baneblade cannon replaced with a giant pus-cannon, which bathes a large area with a contagion that causes the body of whoever's afflicted by it, to erupt in boils and their flesh broken down before their very eyes in seconds.
There is no official Plaguereaper model; official pictures of it depict an excellent conversion by a GW employee.
The Shadowsword is a titan-killer. With a D-strength Volcano Cannon, and the ability to upgrade its BS, the Shadowsword has a very good chance of bringing down even the biggest of titans. This guy is your friend. It will be there for you when something absolutely must die and must die now. GW and Forgeworld both make kits for these -- the GW kit can make seven other tanks, but FW's kit has a bigger engine and a bipod for the cannon to rest on.
The Forge World Stormblade is armed with Plasma Blastgun, a plasma-hurling death weapon that eats MEQ's, hordes, hordes of MEQ's, and even light tanks for breakfast. With better range than the Stormlord and a blast radius so big that Plasma Siphons feel even worse about existing, it excels at killing hordes of anything in Apocalypse. Even vehicle hordes.
The Stormhammer had an official datasheet on GW's website for a while (the page with all the datasheets disappeared after the release of 6th Edition), but no official model, most likely because GW would either need to make a separate twin-turret hull for a single model, or think of even dumber names for another six variants.
The Stormlord is designed with but one purpose: to skullfuck MEQs. With the most dakka seen in Imperial armies (hell, ANYWHERE) in the form of a Vulcan Mega-Bolter (that can fire twice if the tank sits still), the ability to have up to 20 of its 40 passengers fire from its fighting platform and the option to have four lascannons, this tank WILL FUCK SHIT UP. Point at something that's un-fucked, and the Stormlord will fuck it. With its massive cannon. And NO lube.
The Stormsword excels at city fighting. It is able to turn entire building blocks to dust with a single shot. The tank's main weakness is the short range on its Stormsword Cannon.
 Dawn of War series
In the Dawn of War PC game the Baneblade is the IG super-heavy unit, equivalent to the Chaos Bloodthirster Daemon, or Eldar's Avatar of Khaine. Only it's better because instead of a winged Daemon cow or a big flaming dude in a loincloth, it's a fucking giant tank. It is literally the best of these master units in the game, and it will go toe-to-toe with any other such unit and kill them before they kill it. Every time.
Its a well known fact that the crew members of Baneblades are chosen exclusively on the grounds of how big their balls are. This makes them able to shout "Failure is the weakness of the enemy!" "Releasing ELEVEN barrels of hell!" and "All guardsmen, Follow ME to GLOOREEEEY!" and being the only badass non-Hero unit in the entire Imperial Guard.
 DoW II
The Baneblade was introduced in DoWII's latest expansion: Retribution, as the Imperial Guard's super heavy unit and one of the superunits, a title it shares with the Swarmlord, the Great Unclean One, the Avatar of Khaine once more (notably, the Avatar along with the Baneblade are the only returning superunits from the first Dawn of War series), the Battlewagon, and the Land Raider Redeemer (which is a different variant from the one in Dawn of War). It makes a centerpiece appearance in the second mission of the campaign where a renegade one chases your characters around while the crazy Scottish driver yells "IDDACARE WHOO YOU ARE! FELL DA MIGHTA'DA BANEBLADE!!" It then gets sodomized by rudimentary anti-armour turrets. On the upside, if you're playing space marines, you get to watch the Emperor's Fury running around a jungle path being chased by a giant tank (Benny Hill music optional, but encouraged).
It's still a moving fortress of rape that can decimate multiple tanks at a time and blow hordes of enemy units to bits and the strongest and toughest vehicle in the game (since it can't transport infantry like the Battlewagon and Land Raider Redeemer, it compensates with more firepower). The main difference is that while its main weapons systems (the BEHNBLADE cannon and the Demolisher Cannon) do much more damage than before, they don't function like the rest of its guns, they're used for special abilities that require manual targeting to fire, and cannot be fired at targets within minimum range. On top of that, this Baneblade has only TEN BARRELS OF HELL: the co-axial autocannon is there but is non-functional, which considerably reduces the overall firepower of this beast. Needless to say, the Baneblade requires a ton of support to use effectively, or otherwise it will be taken down in melee/at close range by just about anything (though all super units need support as well, so that's nothing new). Also, it's size means it can have difficulty maneuvering on certain maps (DoW II maps tend to not have as much open space as the original's).
The Baneblade has achieved a bit of a mini-meme status because of Captain Apollo Diomedes of the Blood Ravens, who has this tendency to scream: "EET IS THE BEEEEHHHHNNNBLLADDDE", in the most awesomely hilarious voice possible, whenever he sees one. Unfortunetly, this meme is already old and overused.
 The Novel
The novel, titled Baneblade, is about lt. Lo Bannick and his quest to redeem himself from the grievous sin of killing his cousin in self-defense. He does this by signing on to the nearest imperial guard unit and starts the novel commanding a squadron of Leman Russes and then after an Ork ambush he gets a spot as third gunner on the Mars Triumphant.
In short it's written so you could fap to how awesome the Baneblade is.
 External Links
General Sturn likes it hot and heavy.
Make a compensation joke at your own expense.
The track is broken and the sponson turret has a beef with the driver. This is an official image, by the way.
Yarrick's fortress of WHERE ARE MY PRUNES
Multiple Baneblades. Start panicking. Neh, that must be Vance Stubbs missing Baneblades