Grab Bag
This started out as a language grab bag where each student had to pull out a magazine, a paper, or a text book, etc. and reference it properly as if they were writing a theme paper. Other leaders realized that this idea could be adapted to objects that have to be identified and explained in a Biology session or word problems on cards in a hat for Math sessions. The options are bound only by your imagination. The intrigue, of course, is in not knowing which one you will pull out.