Haha I have a few car related.
The wheel weights on the inside rim works well.
Stuffed a bunch of rags and paper in a mid 80's Firebird air cleaner so that it had enough airflow to run fine at idle but die at upper rpms as well as pouring oil into the muffler works well. Had the guy call the shop(his was in college in the automotive program) wondering what was wrong with his car, it had no power and was smoking real bad. Told him to come back and we "checked" the car out. He wasnt amused to see the stuff in the air cleaner, lol. Dont think he ever figured out it was us.
The usual grease under the handles and on the exhaust did well.
Had one trick that was kind of dangerous so dont try this at home. Get a metal can like a paint thinner can, small about a liter size or so, use a flammable gas like oxy/acetyline or propane, fill up can with gas, rtv a spark plug in hole where cap screws on, place on metal frame or whatever under hood and place spark plug wire on plug. When its cranked it makes a horrendous loud boom.
Swap plug wires around, works best with older vehicles of course.
Run a coil wire to the metal frame of a bench seat or bucket seat if possible, will get a nice jolt on the but or legs. Never tried this but was told it works.
Pour oil down arb on a car that sits a while, everytime they person parks it pour the oil in the carb. Had one guy think his 326 Pontiac was blown after doing that a few times. Was even looking for another engine, lol. We fessed up before he got that far though.
In college I was on the parking lot side of the dorms. I knew the people that we did this to. I would call them at all times of the night and in disguised voice say I am so sorry but I backed into your car and broke your tail lights out or similar. Then told them Id be out by their car to talk with them and get insurance stuff done. Of course Id be watching from the window of the room watching guys in their robes or whatever looking over their cars in detail looking for the "damage" and cussing. Never did fess up to any of them, lol.
Had a couple old cars that I had a James Bond smokescreen hooked up to. Id use an old windsheild washer resevoir and pump filled with atf(smoked the best) and a small hose ran to right above the carb throat or tbi throat. When I pushed the windsheild washer button it would dump atf into the engine and make a thick white cloud of smelly stinky smoke. Bad enough that people behind me had to stop or had to turn on their lights to get through. Never had tailgators back behind me for very long either, lol.
Zip tieing the driveshafts with long zip ties works well from what I have heard.
Raw shrimp in air conditioners in buildings works, lol.
Smearing stinky cheese in radiators makes the car smell horrible after warming up.
Tieing assorted objects under car with strings is fun to, when they drive off they hear all kinds of noise.
On older cars replace the coil wire with a piece of rubber hose, looks like a wire but is only a nonconductive rubber hose, lol.
More but this is too long allready.
