This was payback for a coworker putting a banana peal in my desk drawer

I put a speaker in the edit bay he did most of his work in, I hid it in the drop down ceiling. Then I ran a wire all the way back to the Eng Shop and hooked it up to a frequency generator and set it to emit a barely audible high pitch tone, just within hearing range. For the next two months it drove him crazy, he would come back and complain and when I would go to "check out the problem" but on the way out of the shop I would flip a switch I had conveniently placed by the door shutting off the tone, so when we got there the tone was gone, but it would soon be back. After about a month I slowly turned up the volume he still couldn't figure one where it was coming from, finally one of my coworkers ratted me out.

He was VERY upset when he found out, I just told him that he started things, and if he expected that I wouldn't retaliate he now knew just how wrong he had been.

Bwahhh hahhh hahhh (evil laugh)