Red Corsairs on account of being daemonically allied superhuman space pirates. Also, for being a rare example of a major M41 Chaos Space Marine faction not around during the Horus Heresy.
Beyond the 4 main Legions it's up in the air for me. If I had one it would be The Children of Horus. I'll be voting Alpha Legion.
Nightlords have to be it for me. I love the raptor cults - especially how they are portrayed in the night lord books. A distinct subset that even the other nightlords find a little bit off-putting. It would be cool for Nightlords raptors to be a specific class different from other chaos raptors.
Man that's a tough choice. I'd have to go with Night Lords. They strike fast and hard with their forces and are as dangerous at night.
Word bearers, Iron Warriors, World Eaters, Blood Gorgons As long as any of them are in the game, then I'll be satiated. Although I'm pretty sure word bearers are confirmed considering the fact they're seen the concept art on the homepage...
