Command & Conquer 3: Tiberium Wars + Command & Conquer 3: Kane's Wrath = 3 keys
Torchlight 2 = 3 keys
Serious Sam 2 - 1 key
Death Rally - 1 key
The Binding of Isaac - 1 key
Binding of Isaac: Wrath of the Lamb - 1 key
Just Cause - 1 key
Rome: Total War Gold Edition - 1 key
Sid Meier's Civilization IV - 2 keys
Terraria - 2 keys
Amnesia - 2 keys
Dungeon Defenders - 2 keys
Garry's Mod - 2 keys
Half-Life 2 - 2 keys
Syberia Bundle - 2 keys
Bastion - 2 keys
Alan Wake - 2 keys
Magicka - 2 keys
The Showdown Effect - 2 keys
Bioshock 2 - 3 keys
Counter-Strike: Source - 3 keys
Deus Ex: Human Revolution - 3 keys
Serious Sam 3: BFE - 3 keys
Sid Meier's Civilization V - 3 keys
GRID - 3 keys
S.T.A.L.K.E.R: Shadow of Chernobyl - 3 keys
Trine 2: Complete Story - 3 keys
Killing Floor - 3 keys
Title says it all!
Show me some interesting stuff :)