THE worst thing to do to a car is to put bleach in the gas tank. they showed it on mythbusters, the entire engine got fucked and stopped working
altho getting into someones gastank is tough since most cars have it locked up
id say just put up gay personal ads everywhere
or post up his phone number and name on street lights and everywhere so random ppl can phone him up
me and my buddy put one of my frnds phone numbers on a coffee cup at school and left it there.....that night, some random drunk dude called him up
gold