My next door neighbors were having a party and playing really shitty music at maximum volume across the street... at 3 in the morning, had been since around 10PM or so. I could feel the damn bass from nearly 100 feet away. Around 1AM, when I was going to bed, I went over and asked them to turn it down, as politely as possible. They, of course, ignored me and went on playing it. I called the cops on them, got them fined. Also, 2 weeks later was July 4th, and I had a decent stock of fireworks. I took a pair of blockbusters the on the 3rd of July and set them off in their lawn at 4AM. From the shouting about a minute later, I'd say they were livid.

I know, I'm an asshole. It felt good though, and they couldn't prove anything even if they knew it was me.