Cadian Shock Troops - For those who do not know Cadia is basically the gate to the Eye of Terror which in the 40k universe is hell. That's right, Cadian Shock Troops guard the gates to hell and are under constant assault from the forces of hell. These are the men that most other regiments try to emulate and most fail to reach their level as these men and women fight the greatest threat to the Imperium every day and are even so militarized as a people that the regular civilian fashion is urban camo.
Catachan Jungle Fighters - Imagine the most lethal jungle you can, things so lethal that some species are believed to be related to tyranids and most plants are carnivorous. Now imagine that this jungle killing field of death to anything covers a whole planet and you start to imagine Catachan, now imagine the kind of soldier this place breeds, a planet classified as a death world with creatures so toxic rebreathers are ineffective. That is the Catachan Jungle Fighters, the undisputed best jungle combatants in known space carrying bayonets, machetes, and swords that Orks prize if they are able to pry one from the cold dead fingers of the guardsman they had to kill to acquire it, men who repeatedly earned the respect of those orks for their combat prowess.
Tallarn Desert Raiders - After their world was virus bombed eradicating almost all life the forces of Tallarn spent most of the Horus Heresy fighting Chaos Space Marines and their allies on their homeworld in the largest tank battle ever as to step outside meant death due to the now poisonous atmosphere. Managing to defeat what should have been a far greater foe the Tallarn Desert Raiders became one of the best fast moving guerrilla fighting forces in the Imperium thanks to their superb armored units. This takes nothing away rom their feared infantry who can seemingly appear and strike swiftly and viciously before disappearing once more harrying an enemy with guerrilla warfare until he bleeds dry.
More coming