[Lucid:]

in a nutshell, a bunch of people sign up, and two are randomly selected to be werewolves/mafia/some form of killer. they kill off one of the townspeople nightly, while every day the townspeople try to figure out who's killing them off and they hang whoever they think the perpetrator is.
game ends if both killers are hanged, or if the killers take out the entire town.

http://en.wikipedia.org/wiki/Mafia_(party_game)