my favorite form of revenge was a couple of years ago on my best friends ex who cheated on her and was generally a moron. my friends and i were all 18-19 ish so, as you do, went out in town quite a lot to pubs/clubs etc. the weekend after he dumped her we bumped into him in town where he was being particularly cocky and big headed trying it on with anything with a pulse, especially when he knew my friend could see. to put a stop to this we got my friend's step mum to phone up the pub and tell them she suspected her under age son was there, most likely using his older brother's driving licence as fake id and give a detailed description of him (the ex). fortunately our town is quite small and the staff at the pub totally believed it so we continued to follw him round every pub and bar until he was asked to leave them all and couldn't go back to most of them for a long time until they had forgotten who he was. and as an added bonus most of the girls he was trying to chat up thought he was an underage idiot and wouldn't touch him with a barge pole. it was a lot of effort but totlly worth it. unfortunately we're now a little old for that to work so probably won't be using it again!