Materials: none
3 people are selected and go outside (leaders or students who will be keen to speak up front). One of them must have a good story to tell, they share this with the other 2, then one by one they randomly tell the story, but say it as if it was their story. The crowd have to figure out who the story actually happened to. Whoever gets the most votes gets a prize.
Variation: you can also do this game by having one person tell a truthful story, the other two make up different stories and people then have to vote on which one was the truth and which was a lie.