Relax guys, keep it cool. There is absolutely nothing wrong with role-playing. On topic - Blood Angels, honestly.
Blood ravens... cause they are an abomanation done by THQ (I'm sure they where controlled by chaos also).
Ultramarines, the most loyal sons of the dead Emperor. Those goody goodies will serve only to have their souls fed to the Warp.
but but... well I'll set some blood raven paper targets up for you to shoot at then. At least we can imagine that we are wiping them out.
i would like to purge the land of every race with my emerald gauss, but since this is a chapter pick, im gonna say ultramarines. They are just used too much int he game series.
Space wolves. They are even more arrogant than Ultramarines. And just because there is nothing better than flayed emperor's curs.