I have left the original intact. This expands upon the original idea, and could be well called a sequel.
How to have phun with someone else's car. If you really detest someone, and I mean detest, here's a few tips on what to do in your spare time. Move the windshield wiper blades, and insert and glue tacks. The tacks make lovely designs. If your "friend" goes to school with you, Just before he comes out of school. Light a lighter and then put it directly underneath his car door handle.
Wait... Leave... Listen. When you hear a loud "shit!", you know he made it to his car in time. Remove his muffler and pour approximately 1 Cup of gas in it. Put the muffler back, then wait till their car starts. Then you have a cigarette lighter. A 30 foot long cigarette lighter. This one is effective, and any fool can do it. Remove the top air filter. That's it! Or a oldie but goodie: sugar in the gas tank. Stuff rags soaked in gas up the exhaust pipe. Then you wonder why your "friend" has trouble with his/her lungs. Here's one that takes time and many friends. Take his/her car then break into their house and reassemble it, in their living or bedroom. Phun eh? If you're into engines, say eeni mine moe and point to something and remove it. They wonder why something doesn't work. There are so many others, but the real good juicy ones come by thinking hard.