This is extremely fun in improv. It's a classic game and it's quite tough in real life. We all stand in a circle and the improv leader picks 2-3 assassins and they go around killing the civilians. They can kill the sheriff if they find out who it is.
The best part was that if the civilians picked the wrong guy, depending on how many people voted for him, he could die (lynch mob). Great stuff. I'd love to see a server with this on it.