I asked this same question on Yahoo! Answers and generally got the morally righteous answer of 'move on'.
But fuck that. I know you newgrounds users are more sinister so this is how it went down...
This person who I was fairly friends with did something to me which made me look like a complete idiot in front of tonnes of people at my sixth form college. Obviously I felt angry at him and want to get back at him since it was completely unprovoked.
Yet I know the best advice for situations like this is 'move on and enjoy your life, as this will anger him more than anything you could do'.
While I understand this, it's almost a matter of principle. I know he feels no remorse for what he's done, and I want to teach him a lesson as well as prove I'm not a pushover.
All sorts of activities both legal and otherwise have gone through my head, what should I do?
Also, I know where he leaves his car during the day.