I don't really do revenge
But a couple of friends did something to one of the guys on my floor when I was in halls, for some reason, as yet unidentified.

He had a tendency of leaving his door unlocked - not a wise thing to do, but security risks aside, these two guys decided to take advantage of the situation. Every object that could be moved was turned upside down - every single book on the shelf (but not the shelf itself, being screwed into the wall), the hi-fi, speakers - even the posters on the wall, down to the sheets on his bed, were turned upside down.

Of course, the guy in question never left his door unlocked again, and for months afterwards, he was still turning things the right way up.
(witty_ditty has made multiple miaows since, Fri 14 May 2004, 12:11, Reply)