I recollect a certain graduating class of seniors at one of my old alma maters were fond of chemistry, and as such, they decided to make some Th3rm-ite, lay it in a perfect circle on the frozen pond next to the school and proceed to burn a perfectly round hole in the middle of the lake.
I have no idea if this actually happened (well before my time at school there), but it does make sense as each graduating class since then has had to prank in some 'magnificent' way. My graduating class? I can't say what we did, but it wasn't as glamorous. Really sedate comparatively, though my roommates were both super geeks, one was a Pre-Med / Math Double Major, and the other Computer Science / Physics Double Major. I was the idiot who got sh1t done. Art / Business. So, I was the guy who skipped class, never bought books, and stayed home to build bunk beds on one side of the suite, then build a bar and entertainment space on the other, by myself, in one afternoon.
Freaked them out when they got back from class. It was a sweet setup.
We used to do some funny pranking to one another using m3r-cury switches and battery operated water pistols, and other gadgets we could rig for a surprise.. All in good (wet) fun. Radio Shack used to be a cool place to get stuff for our projects.