I'd say the worst thing I've ever done was helped my friend steal my Gym Coaches iPod while he was watching the kids run laps. :U!!
Luckily I didn't get caught, he got caught though. >:3!!
Edit:
He also found some paper with everybody's locker combination's on it. He stole a stuffload of phones, a couple iPods, some money, a PSP, some research O.o , alot of pencils, homework, and everyone's hall passes, which he sold all off at school, until someone reported him.
It was actually quite organized. I didn't plan on taking any electronics though, he did that, I just wanted the hall passes to sell...
I've changed though since then. Trust me. :c