I'm sure I'm going to list some of the games already said here but,
Just Cause 2 (Shooter)
Saints Row the Third (Shooter)
Borderlands 1&2 (Shooter)
Command and Conquer Red Alert 3 (RTS)
PAYDAY the heist (Shooter)
The Ship (Mystery 'Shooter')
Terraria (2D Platformer Adventure)
Minecraft (3D Platformer Adventure)
XCOM: Enemy Unknown (TBS)
The Wonderful End of the World (Uhhh...)
AaAaAA!!! - A reckless disregard for Gravity (Freefall Hoops Game Thing, also flip off supporters and thumbs up protestors for confusion)
Alien Swarm (Top down Shooter, also free)
Portal 1 & 2 (Puzzler)
