Man, i remember high school science projects, they were awesome. I always had some of the most interesting in class. One year i made a homemade rocket launcher. I got a big tubing (like for holding drafting paper or paintings), made it into a rocket like launcher, then went to a hobbyshop and got some homemade rockets. Put them together, and put the rocket in the tubing. I had rigged the 'launcher' with my old RC car battery, so that all i had to do was connect the connection (by depressing a button), and it would fire off.
The first time i fired it in my backyard, i got a face full of chemicals from the rocket when it exited the tubing, so after that i made a plastic shield to protect my face. But inclass when we had to do it, the whole class went out in the yard with me, and i fired it off a good 50 feet. I got asked to come back to 2 other of his classes to demonstrate my project too.