Left 4 Dead is the ultimate coop zombie survival game from Valve that delivers on fast paced action. Work together or alone, online or offline with bots as you battle hordes of zombies. Fight through iconic locations with small teams as you bash your way through the undead. There are other modes aside from the general campaign including Versus or Survival. The games are greatly expanded upon with mods on the PC side of things and they're generally a staple on Steam.