DayZ
DayZ is a gritty, authentic, open-world survival horror hybrid-MMO game, in which you follow a single goal: to survive in the harsh post-apocalyptic landscape as long as they can. There are no superficial tips, waypoints, built in tutorials or help given to players. Every decision matters, there are no save games, no extra lives, every mistake can be lethal. If you fail, you lose everything and you need to play again from the beginning with nothing but your wits, and your two hands. Fight the hostile environment, where every other player can be friend or foe and nothing can be taken for granted. This is DayZ, this is your story....
Left 4 Dead 2
Left 4 Dead 2 is a cooperative first-person shooter video game, the sequel to Valve Corporation's Left 4 Dead. The Game builds upon cooperatively focused gameplay and Valve's proprietary Source engine, the same game engine used in the original Left 4 Dead. Set during the aftermath of an apocalyptic pandemic, Left 4 Dead 2 focuses on four new Survivors, fighting against hordes of the Infected, who develop severe psychosis and exhibit zombie-like tendencies. The Survivors must fight their way through five campaigns, interspersed with safe houses that act as checkpoints, with the goal of escape at each campaign's finale....