Oh, there's another one... stole supplies from the chem lab to make our own gunpowder. Made a big old batch of it. Then we took one of those big popcorn tins from the holidays, set a fire in it, and then threw handful after handful of black powder onto it. It was fun, and looked really cool...
Not that well thought out, as my room at the time had a wood panelled, angled ceiling (since it was on the top floor). The flames were shooting up a few feet, but luckily not enough to catch anything on fire. Everything in the room was then coated in a layer of soot, and we were coughing up black stuff for days. Oh, and the popcorn tin melted a patch on the carpet that I subsequently blamed on the cat. I'm sure the parents didn't buy it, but couldn't figure out how I actually would have done it.