Crassus Armored Assault Transport
The CRASSUS ARMOURED ASSAULT TRANSPORT is one of the heaviest armored transports available to the Imperial Guard. Though it does not carry as many soldiers as the Gorgon (with which it seems to share a chassis, as well as the Macharius), the CRASSUS ARMOURED ASSAULT TRANSPORT is fully enclosed and armored all around.
Plus the Gorgon suffers for simply not being the CRASSUS ARMOURED ASSAULT TRANSPORT.
Praetor Armoured Assault Launcher
Much as the Chimera was modified into the Manticore Rocket Launcher by adding 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.
Considering that the Praetor launcher has no limit on ammunition (during the game, anyway), a comparison to the Rhino-based Whirlwind might be more suitable.
Dominus Armoured Siege Bombard
Another variant of the CRASSUS ARMOURED ASSAULT TRANSPORT the DOMINUS ARMOURED SIEGE BOMBARD replaces the troop transport capability with a battery of three Dominus Triple Bombards. This turns it into a dedicated artillery that can rapid fire due to its automated weapon system and the fact that it carries not one, not two but THREE artillery pieces meaning that it can devastate entire blobs of armies in a single phase. It's very much the Wyvern's bigger brother and shares largely the same set of targets as it.
Unfortunately it sucks at close range and will need ample protection if enemies get too close.