I used to have a noisy downstairs neighbor. After months and months of talking to them face to face, posting friendly requests on their door, and involving management to help (with video/audio/picture support), nothing changed. So the wars began.
They were the worst. They were always yelling at each other. They played music very loud at all times of the day and night. He had some kind of woodworking tool on his deck (not allowed) that was very loud. He used it daily. He did demolition derby and always had some junker he was repairing in our parking lot. She would get into long, super loud conversations on the phone. The works.
So, they have this kid. Maybe 2 years old, and she's as much of an asshole as her parents, probably, you know, because she has to live with them.
To mess with them, I did some fun things. First I invested in some Winchester noise canceling headphones. Then I put my refrigerator on baking sheets and it rattled loudly. I didn't notice because of the headphones, and they constantly sent building maintenance up to talk to me. It got bad enough that we were all given notices that said "fallacious maintenance requests will be charged a $40 penalty".
I put a bunch of coins in my drier and put it on "wrinkle free" which keeps turning it on every few minutes - I'd activate it when I left for the day. This gave me tons of angry post it notes from them, which I gleefully stored in a folder that I've since lost.
I ran an extension cord off my deck and installed a light socket-to-outlet converter on their porch light (he used big ole' halogen lamps, and never used his real light) and plugged a lot of things into it, stealing their electricity. I probably saved a whole $2. Fuck that guy.
And I also took up some weight lifting workouts. And by weight lifting, I kinda mean couch-dropping. When they put their kid to sleep, I would drop my couch a good 3-4 times in a row until the kid started crying and the couple started screaming again. I'd also drop it when they were asleep (8 am - 4 pm most days) until they screamed and thumped the ceiling... And then I would set a 15 minute alarm to remind me to do it again once they were likely asleep again.
I took up gardening. I had a bunch of garden plants on my porch. I'd water them anytime he tried to use his wood working thingie. I bought a super long hose attachment for my sink, designed to be used to clean a fish tank.
I learned their routines, and would run all my faucets at full blast on the highest heat for a half hour before their shower time. I was on the 4th floor, them the 3rd, and we were on the edge of the property. Hot water had trouble getting to us sometimes.
I also had some digital wireless headphones. Push a button and they would cycle through frequencies until they found something, which was normally the base unit attached to your music device. But they could also pick up a landline's wireless receiver. So, this is wiretapping at this point, and I would listen into mombitch's conversations and learn all the ways she reacted to what I did. It was glorious. And sometimes she'd let slip, "Well, at least we can still do X without the fucker upstairs bothering us." NOT ANYMORE, WHORE. And then I'd go bother them in a new way.
The car was one of the hardest things for me to deal with. He would come home late at night with a truck and a trailer (which wasn't allowed on the lot). He'd park the truck, get into the car on the trailer, and go park the car. Then he'd come back and move the truck, and leave to park the trailer.
He wasn't allowed to have the trailer, and after most nights the car could be considered derelect - dented, damaged, no glass, not street legal, etc. So I made friends with the local tow company, and called them once every few weeks. Sometimes they'd grab his junker. Sometimes they'd grab his truck, which he always left idling with the trailer (Hint: there's no truck-with-trailer parking because you're not fucking allowed to have a trailer in the tiny lot!) Either way, each time he got towed he also got a bill from the landlord.
I also cost them over $500 in under 6 months by reporting minor contract breaches on their part to the management. The landlord wouldn't kick them out, but they'd damn sure nickle and dime them to death.
In the end, I renewed my lease. The months of warfare was invigorating, and gave me tons of fun stories. My noise canceling headphones blocked most of my counter sounds, and with them on and some nice quality earbuds underneath I could hardly hear their racket anymore. Add some white noise generators, and really I was pretty much relieved of their annoyances. About 2 months into the new lease of mine, CPS took the kid away (which needed to happen, that place was abusive as fuck), and they got kicked out of the complex. You see, he had taken up weed to calm his nerves.... and I don't like bad smells.