Need to get my little brother a steam game for christmas. Any recommendations?

[JoshGod]

Well as he likes shooters;
Fear (the first and maybe second)
the Metro series
Shadow Warrior
Call of Juarez Gunslinger
Serious Sam
Spec Ops the line (tps all the games you listed are fps)
Borderlands (the second is better, but we're still waiting for more dlc >.<)
Transformers (either)
Bulletstorm (has gfwl)
Bioshock (any)
Warhammer 40,000 Space Marine (more of an emphasis on melee combat but has shooting, and awesome)