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.
Lots of fun with friends but tends to be a bit dull alone. I also find it harder to play as the human who only gets one life than the zombie who can re-spawn.