Catachan

Catachan live on a 'Death World' which is basically earth-hell since you can be killed by pretty much everything including the god damn flowers. Every animal is either carnivorous and/or poisonous, how said ecosystem manages to survive with no prey creatures is anyone's guesss.

Basically the Imperial Guard's version of Rambo/Schwarzenegger hybrids, based on US Army/Marines and South Vietnamese ARVN/Marines during the Vietnam War. They're supposed to be the toughest motherfuckers in town (next to the Tanith First (And Only) of course) they actually figured out that wearing some silly flakarmor jacket was completely useless so they go in and fuck shit up all manly like.

With knives, guns and flame throwers.... And sometimes knives attached to guns, and knives attached to knives attached to a gun. Or just punching things in the face till it dies.

The Catachan are also considered one of the most badass regiments out there, because their abs give them a 5+ armor save. Sometimes, they can get a 4+ armor save, if they wax enough.

Noted to be one of the few worlds in the Imperium where black people exist.

It should also be noted they don't like commissars that much...Usually most commissars end up "accidentally" walking into a Catachan trap