Here is a great, low cost idea that can be used as a stand-alone game or used with the accompanying devotion. YouthWorker Circuit is a great resource site, run by some great youth workers, including @gavoweb.
Here is a bit about the game:
Whatever the time of year it is in youth ministry there is always a need to have some youth group games you can pull out at a moments notice. One of my all time favorite youth group games is one I call “Identity Crisis”. You can pull this out in a pinch or plan for it during a retreat. The game can take 30 plus minutes each round depending on how creative and into bluffing the youth are.