play Mafia. Due to the fact that it was a large group (probably about 15-20 people), that we were outdoors without easy access to pencil/paper, and the fact that the number of players changed from game to game, we just had the narrator pick the roles rather than drawing from a bowl or hat or something.

After a few rounds of being the narrator (or moderator, however you called it) I decided to have a little fun with the group. I didn't choose anyone to be the mafia. At the beginning of each round, I acted as mafia and decided who would die. Of course during that time the dead people would frantically look around to find out who the mafia was. When they realized it, I put my finger to my lips and, surprisingly, none of the dead players gave it away. By the time there were only a few players still alive, they were down each other's throats so much (and I think I even chose the most vocal people to keep alive at the end). Eventually it got to the point where it couldn't be kept a secret anymore, and I confessed. It was very entertaining to watch, though, especially as there were only a few left and they were freaking out, questioning everyone and everything they thought they knew about each other.