[Jeff The Ninja]

Counterstrike sucks, avoid it like syphillis.

Half Life 1, 2.
MDK
Resident Evil series (works suprisingly well with a keyboard)
DOOM
Duke Nukem 3D and Shadow Warrior
Diablo 1 and 2
Warcraft (NOT fucking world of warcraft, if you play WOW, you live a wasted life)
Clive Barkers Undying
Monkey Island
Unreal Tournament
Grand Theft Auto (also good on the PC)
Stonekeep (ruled my life as a child)
Batman Forever (I dont care what you say, it was fun to bust heads)
Sango Fighter games

and dont forget

CRUSADER:NO REMORSE
CRUSADER:NO REGRET

Two of the best games ever made