This game went viral on youtube some time ago. It wasn't much of a game then but with a few easy steps, you can turn it into a fun game that will also provide for great photo ops. I strongly recommend you play this if you haven't yet.
1. 50 or so rubber bands.
How to Play:
Bring several students up. Explain to them that the object of the game is to fit as many rubber bands over their face as possible in the allotted time limit. Do not tell them how long you're going to go for. The winner of the game will be whoever has the most rubber bands on his or her face when time is up. It's super simple but will be fun and will definitely make the audience laugh.
End the game before all the rubber bands are used and before people get bored.
Choose several judges and tell the contestant they'll be judged on: number of rubber bands, style, and face coverage. This alternative adds a small amount of complication but will be a little funnier and more photo friendly.