Zombie Panic!: Source

Zombie Panic! Source is a zombie apocalypse-based modification of HL2. It is a multiplayer game for the PC where collaboration between survivors is crucial for success. The beginning of any game begins in a room where one can choose to either be a Survivvor, a zombie, or a spectator. The majority of players choose Survivor, despite the zombies advantages of respawns, zombie vision, and higher health. After a set amount of time, the game begins. If there aren't enough zombies for the game, a Survivor(s) is randomly chosen to be zombie. Survivors can win by either killing off all zombie lives, or by finishing certain objectives. Zombies win by killing all humans.