SAS: Zombie Assault 4

Action, RPG, Free to Play — Single-player, Multi-player, Online PvP, Co-op, Online Co-op, Cross-Platform Multiplayer

Purge the undead! Intense action-shooter with deep rpg elements, including upgradeable guns and armor, unique class skills, and class special abilities. Entire game can be played single player or as a 4-player online co-op game, including PvP events like Last Man Standing.