Zombie Panic! Source is a standalone cooperative, survival-horror, first-person-shooter! Set in the middle of a zombie apocalypse, players start as a small group of survivors attempting to stay alive. Each map will have its own objectives to complete and win the round or survive by a period of time.
A unique multiplayer experience. You'll start playing for the zombies and atmosphere, but you'll stay for the endless amounts of fun you'll have with the community. Although it ends up being more of a comedy than a horror, I'm totally ok with that. Its like the best bad B movie ever.