.....also - stick a block of LARD on the keyboard of his new laptop and close the lid....hmmmmm won't close properly? You may have to squash it in then........
If you can get into his flat when he is away then dial the USA TIm and leave the phone off the hook. Let his tyres down. Put his details in a phone box as a stud. Superglue his doorbell - or anything else you can get to. Put a few tacks just in front and just behind a couple of his tyres so whichever way he goes they go in. Wedge a spud up the exhaust pipe. Send his details to every catalogue and spam provider you can find so that he gets loads of stuff. If you have a spare key to his car and can keep moving it, altering the seat etc that will be a problem to it. A friend filled "his" car with horse manure. The other good ones have already been mentioned. You can put cheese in the curtain hem too. Not that I'm a malicious person though.... But maybe the best revenge is to show that you don't give a F***.
ssquirrel, just an observation but i noticed that on friday night at 10pm on sky channel Five Free (or summat?) there is a programme all about revenge on your ex.......... you might get a few more ideas! : )
Post an unbelievably good ad on Gumtree for something like a flat and he'll be harrassed with endless flat hunters calling up about the flat. You could make even put a few different ads on eg car, washing machine, puppy, weekend in paris, date, job etc.
Thank you all so much for your answers. Brilliant!!! Particular thanks to Raysparx1. Love the Foam/car thing oh so very tempting. Not sure I want to see his body float down the river just yet. Think I will go with the Ad idea. It has such great long term potential and would it this ex-relationship.