I’m not sure how many schools do this anymore, but back when I was in my younger years we always had a Build an Elastic Band powered Fan competition, where each contender would be racing against each other to build a fan powered by using an elastic band, a spool and a pair of plastic blades. :)
Complicated stuff I can tell, as these girls appear to be having a spot of bother:
http://gamesprays.com/files/resource_media/preview/texas-style-6422_preview.png