HaLO 2 (sequel to one of the best games ever)

Halo® 2 is the sequel to the highly successful and critically acclaimed Halo®: Combat Evolved. In Halo 2, the saga continues as Master Chief—a genetically enhanced super-soldier—is the only thing standing between the relentless Covenant and the destruction of all humankind.

Check this game out it's awesome

Check the links out

Halo: Combat Evolved
http://www.microsoft.com/games/pc/halo.aspx

Halo 2
http://www.xbox.com/en-US/halo2/