Buying a Gaming pc, what are your TOP 10 must have pc games?

Call of Duty Modern Warfare 2

Bioshock

Killing Floor

FarCry 2 (sorry, multiplayer is dead with this one, but campaign is long)

Half Life 2 and Episodes 1 and 2

Team Fortress 2

Portal

Left 4 Dead

Medal of Honor Airborne (good for only being $10 on Steam)