Something evil about force-feeding Word on students who wanted to use MacWrite instead.
But not as bad as some of the other little tricks.
One of the worst was to put an alias to the shutdown command into a Mac's startup items folder. Start up, shut down. Start up again, shut down. Whee! And this was back when startup took a LONG time.
As for Windows, a boss of mine at work put in place a long sound file onto his own PC to replace the very brief error "ding". The sound file was a clip from "True Romance", in Christopher Walken's voice:
"You see that?" *sound of a punch landing* "That smarts, doesn't it? Getting slammed in the nose. F---s you all up. You get that pain shootin' through your brain, your eyes fill up with water. That ain't any kind of fun, but what I have to offer you, that's as good as it's gonna get. And it won't ever get that good again. "
As that clip played it would take over the whole computer. The little hourglass icon was there, and you could do nothing as it played. You just had to sit through it.
And of course, since it was a replacement for an error sound, it only ever happened when something went wrong - when the computer refused to do something my boss wanted, for example.
So the natural frustration of having the computer refuse a command (say, to select something away from an open dialog box demanding his attention) was compounded by the fact that this happened together with a long sound clip, COMPOUNDED by the fact that in context the computer was taunting him and telling him it was only going to get worse. He'd get real frustrated, sit there steaming, as the sound would play over and over again, as he tried to do something.
AND HE DID IT TO HIMSELF.