Zombie Panic!

Zombie Panic! is a multiplayer game and modification for Half-Life in which the human team must fend for themselves against a horde of zombies. It is currently available to all owners of Half-Life, and can be downloaded free of charge. The mod has a creepy feeling to it and is designed to imbue the player with a sense of desperation. Overall, fun and playability take preference over realism and horror. Zombie Panic! must be played with two or more players. When the game starts one player is chosen to join the undead team as the first zombie. This is done by allowing the players to volunteer for the undead team. Should more than one player volunteer, a random volunteer is chosen. Likewise, should no players volunteer, a random player is chosen. All other players are placed into the survivors team. After the players have been placed in the appropriate teams, the round starts.The goal of the survivors is to find the various weapons, and use them to defend against the undead team. The... full article at wikipedia