Are we talking funny stupid or serious stupid? Because I've done both.
I once super-glued every singe door, the gas tank door, and tire seals on my high school principal's car. I wasn't too happy with him on that particular day. They needed nail polish remover and a file to get each door open, but never found out who did it.
Oh, what else have I done....?
I stole the master key to the high school (for fun)
I hacked the security feed for the security cameras in the school and put them on an empty loop
I drove 80 mph down an empty road, and then slammed on the brakes, spun the wheel, did a U-turn, and kept driving (never going below 25)
I got high on sleeping pills and then tried to play the Nintendo Wii (DO NOT TRY THAT)
There are many, many other crazy stupid things I've done.