Here's an Instructables to bring back the obnoxious kid that lives not so far down in all of us: Learn how to turn one of those miniature Altoids tins into a tiny catapult. It'll be fun for nobody but you.
We like Instructables like this one because not everyone has a damn laser cutter lying around, and this one only requires materials you've likely got lying around anyway (coat hanger, rubber band, spoon, etc.). The creator promises it'll only take about 10 minutes, and we promise it'll be fun for at least 11. [Instructables]