Crassus Armored Assault Transport
Named for Borgen Crassus, one of the leading generals of Lord Solar Macharius, the CRASSUS ARMOURED ASSAULT TRANSPORT, a.k.a. the Mark IX Tank IN SPAAAACE!, is one of the heaviest armored transports available to the Imperial Guard. Armed with a quartet of Heavy Bolters and capable of lugging 35 of your t-shirt wearing maniacs/über badasses around the battlefield, the CRASSUS ARMOURED ASSAULT TRANSPORT is essentially the Guard equivalent of the Land Raider, but with fewer guns.
Based on the chassis of the Macharius Heavy Tank, the CRASSUS ARMOURED ASSAULT TRANSPORT is the perfect vehicle for carrying large amounts of Guardsmen directly into enemy fire and dropping them off exactly where you need them.
Even though the CRASSUS ARMOURED ASSAULT TRANSPORT is a relatively new addition to the arsenal of the Imperial Guard, it has already become famous for its heavy armor and firepower, and has entered widespread use in the southern and western regions of the Segmentum Tempestus, and after only a few centuries the CRASSUS ARMOURED ASSAULT TRANSPORT design is now being constructed on the Forge World of Lucius and is used to extensively resupply the Imperial forces that are guarding the space around the Eye of Terror to replace the ongoing losses in that steadily worsening warzone.
Everywhere it had been deployed, the CRASSUS ARMOURED ASSAULT TRANSPORT had earned a considerable reputation for its sheer power and durability. This reputation has given the vehicle near-talismanic status amongst some siege assault units of the Imperial Guard, to the concern of some within the Commissariat and the Departmento Munitorum. The Tech-Priests probably wholly approve, though.
In case you were wondering why it seems like this article is rudely screaming the name of this vehicle at you through your screen, some fellow asked in a DakkaDakka thread about whether it'd be worthwhile getting the CRASSUS ARMOURED ASSAULT TRANSPORT, and they typed its name out in all-caps because they simply copied and pasted the name from Forge World's product list, wherein everything is listed in all-caps. Memes, of course, ensued. Most likely because the name is so long that it really is easier to just copy-paste it... and also to needle the guy for the caps, of course. Still, DorianGray, the Original Poster, is now one of the few and the proud who have actually created a new meme.
Praetor Armoured Assault Launcher
Much as the Chimera was modified into the Manticore Rocket Launcher by ripping out the troop compartment and bolting a missile launcher to the top, the PRAETOR ARMOURED ASSAULT LAUNCHER mounts a massive Praetor missile launcher instead of a transport bay. It can launch Foehammer missiles for cracking armor, Firestorm missiles for blasting large infantry formations, or Pilum (Latin- "Javelin") missiles for anti-air defense. Which is a bit silly since javelins were created to kill infantry, but it could be a reference to the real life Javelin anti-aircraft missile. Although in retrospect, hammers are pretty good against armor, and everyone likes killing things with fire, so it all works out.
Considering that the PRAETOR ARMOURED ASSAULT LAUNCHER has no limit on ammunition (during the game, anyway), a comparison to the Rhino-based Whirlwind might be more suitable. But this bad boy is infinitely more awesome, and in reality it would probably be quite a bit more deadly.
However, due to the vehicle's complexity, it has not been as widely distributed as the more basic CRASSUS ARMOURED ASSAULT TRANSPORT. Servos that rotate something up and down are, after all, incredibly complex, right? Well, not really, since said servos are not only extremely common in Imperial tech but also simple and cheap as balls in real life too. Seriously, the AdMech is just being an ass here for the lulz and using "complexity" as a bullshit excuse. Anyways, while the PRAETOR ARMOURED ASSAULT LAUNCHER'S sophisticated (targeting) systems and relatively high materiel cost make it unlikely to replace or supplant the existing Imperial designs for mobile rocket artillery pieces, its durability and sheer versatility have already ensured it a valued place amongst those Imperial Guard units facing the most deadly adversaries of the Imperium. Which implies that if the AdMech stopped pretending it was difficult to make (ten bucks says the guidance system is the same as every other Imperial rocket artillery) and spams them, said deadly adversaries would be definitively fucked.
An interesting bit of trivia is that the design for the Praetor Heavy Assault Launcher actually predates the introduction of the CRASSUS ARMOURED ASSAULT TRANSPORT by quite some time, and it is believed that the last time the PRAETOR ARMOURED ASSAULT LAUNCHER saw widespread use by the armed forces of Imperium was against the Land-Leviathans deployed by the Tellarite Rebellion forces who had forged a pocket-empire in their little corner of the galaxy during the dark years of the Nova Terra Interregnum. Apparently not even those things could resist the might of the Macross Missile Massacre. Still, the fact that they saw widespread use at all implies that the whole "it's too complex to see wide-spread use" reason really is a fucking lie. As usual, anything that would allow the Imperium to kick ass (or enable the Imperium to outright win the Eternal War with that one thing alone) is not allowed to be used by almost anyone anymore... the Imperium is a true defender of the status quo by virtue of murdering their own brain cells whenever something cheap, useful, and easy to mass-produce comes along.
Dominus Armoured Siege Bombard
Another variant of the CRASSUS ARMOURED ASSAULT TRANSPORT, the DOMINUS ARMOURED SIEGE BOMBARD replaces the vehicle's troop transport capability with a massive Dominus Triple Bombard. This turns it into a dedicated artillery piece that can rapid-fire massive shells due to its automated weapon system and the fact that it carries not one, not two, but THREE enormous mortars, meaning that it can devastate entire blobs of armies in a single phase. It's the Wyvern's bigger, angrier brother with a criminal record.
In practice, the DOMINUS ARMOURED SIEGE BOMBARD throws 3d6 S10 AP3 shots with indirect fire when stationary, easily wiping out any unit foolish enough to be larger than 5 models. S10 AP3 is also a serious threat to any armor short of a Titan, and the sheer amount of shots in the air pretty much guarantees overkill on most single-model targets. Think of it as an entire battery of Basilisks in one vehicle, except for less points, with better armor, no Open-Topped bullshit, and a pair of sponsons to actually defend itself.
One final point of delight in this thing's favor comes from how Overwatch works- Not only does it get to fire everything it has at anything that charges it (which will frequently paste Dreadnoughts when hitting on 6s), but can simply drive out of combat and keep shooting thanks to its Steel Behemoth special rule.
Despite having had rules released for it in the 8th Edition overhaul, the DOMINUS ARMOURED SIEGE BOMBARD doesn't actually have an official model. So expect a lot of fan conversions like the image on the right.