One of the most popular games we play in our youth ministry is a game we learned at Lake Ann Camp called Octoball (I've also seen it refered to as Gaga Ball).  It's a bit difficult to describe, but probably most accurately is an enclosed dodgeball game below the waist.  The object of the game is pretty simple; get a bunch of people inside of the octagon ring and try to eliminate the other players.  If you're looking for a great game to play in your youth ministry, this one is a winner.