I would have to say space wolfs just because they are extreamly loyal and like to attack head on non of this stealthy stuff. Along with that if they ever turned chaos khorn would love them
Nothing against the other legions (especially Blood Angels), but I have to go with Space Wolves; hands down. Simply because it'd be refreshing to see Space Marines in a different way as opposed to the more human-looking bunch we generally get with every W40k game. Salamanders would be pretty cool to have, also.
Space Wolves (Yes, I realize my Pic is the Salamanders Chapter, another favorite). The Space Wolves are my favorite Chapter and nice to get to see them represent in EC (Considering we only got to be the Blood Ravens in the DoW Games, Lame).