This was ~15 years ago. We got a laptop with school credentials on it, but couldn't log in to the local admin account, only our own student network accounts so couldn't do anything fun with it. No problem, install Linux on a flash drive, plug that in, run a script to crack the admin account (thanks rainbow tables) and get in. It was not a very strong password. A lot you can do now. Install games, browse the web unfiltered, and so on, but problem is our use of the laptop was limited to the after school activity we were part of (robotic club obviously) so still not really too much fun to be had unless we wanted to get caught pretty quickly. But there was one thing, we could grab the WiFi password. Turns out that it's only hidden on the student accounts, on the admin account you just click on the WiFi network and it just gives it to you. We didn't plan for it but we didn't take advantage of it. We shared that password to a couple friends but in general kept it under wraps, this was before data plans were so wide spread so it was actually useful, and the school itself was a faraday cage for anything but the weakest cell signal. Best part, it worked in other schools too, so I'm pretty sure it got spread pretty far eventually. I graduated before they changed it, no clue what happen after though.

We also took the balls out of the mice. And put tape on the optical ones.