I just got back from March Meeting, the one of the world's largest physics conferences. I thought I'd share one talk which used relatively basic physics to explain a surprising phenomenon:
Summary for people who don't watch videos: You have a long chain of metal beads in a beaker, and you let the chain fall out. Rather than slithering over the edge of the beaker, the chain jumps out of the beaker. It turns out the explanation has to do with the shape of the beads; when the chain is pulled out, geometry requires that the beaker gives the beads an extra kick.
I think it could be a neat science fair experiment for someone to design a chain which produces a larger fountain. The chain needs to be made of long beads, whose mass is concentrated in the middle. I'm not sure what you would make the beads out of.