Here are some of my ideas. I hope they help.
1. That floss/trip thing was a good idea, but put a pile of dog shit on his front step, too so that he lands in it!
2. Tee-Pee his house
3. Fill a bunch of water balloons with piss, and then throw them at him when he leaves the house for work.
4. Write things on his car or windshield with paint. Some examples: Douchebag, douche, ass, balls, penis, (you could also draw balls and a penis), faggot (kind of offensive though, and not funny if he really is gay), ass hole, ass wipe, cock, cock sucker, i dunno, just get creative with that part. It's up to you what you want to draw or write on his car. You could also do this with his driveway, garage door, or even the side of his house!
5. Fill a bunch of paper bags with dog shit, and then throw them at him or his house
6. A new idea that I've never attempted; take a paper bag, and fill it with firecrackers and dogshit. I think you know where I am going with this. Maybe put some gasoline in the bag (not too much, so as not to start a fire) so all of the fire crackers will go off, and then put the bag on his porch, or next to his car (or better yet, in his car, if he keeps it unlocked) and then light one of the fuses sticking out from the wad of shit, gas, and fire crackers, and then run!
I hope some of those ideas can help you get back at this guy.