What is Carmarking? Ah. It's the process of fatally inscribing something (usually something naughty) on the vehicle of someone who has got your goat. Although there are many methods (keying, Magic Markers, etc.) I will lay out some of my faves.

Warning! Although meant for scientific exploration ONLY, many if not all of these methods are considered vandalism in most parts and can make the practitioner liable to arrest, harrassment or simple anal rape with a policeman's nightstick. Plus, the owner of the car might catch you before the cops get there to save you. So be careful.

The Salami Method

So named for its delivery vehicle, the Salami Method produces a localized pattern of surface destruction. Simply place a medium-thickness slice of salami on the hood of the target vehicle on a sunny, hot day. The preservatives and other nasties contained in this otherwise delectable snack will, over the course of the next several hours, penetrate the clearcoat and paint of the unfortunate chariot. After several hours, the act of attempting to peel off the offending lunchmeat will result in the paint beneath it coming off the car as well. Note:This has not been verified with newer, 'eco-friendly' salami. For best results, old-school Genoa or Hard salami is recommended.

The Borax Burn

Although this is a delightfully fun one to undertake, it is riskier than The Salami Method because it involves combustion. Take a sheet of paper (laser/copier stock is fine) and place it on the victim auto. Using powdered cleanser that contains Borax (Borax, maybe Comet? etc.) write your message of choice on the paper. 'Fuck you,' while a favorite of many, is somewhat unimaginative and fails to convey any subtle nuances of insult that the actor might wish to pass along. In any case, once this is done, cover the paper and cleanser with English Leather, Right Guard, Hair Spray, Ronson Fuel or anything else that will burn quickly. Stand back! Toss a match at the pile and shield your face.

If done properly (i.e. the substances are flammable enough) the paper will burn so quickly that it won't damage the underlying surface. The message in Borax, however, will be burned through the paint and into the very metal of the car, and will be a cast-iron bitch to paint over, requiring many coats. For extra utility, this method also works well on concrete and brick!

The Corrosive Cola Conjunction

This method makes use of one of the lesser-known properties of your favorite soft drink. As part of its witches' brew of ingredients, cola (Coca-cola, Pepsi, RC, etc.) contains noticeable quantities of phosphoric acid. Handily for our purposes, this substance is used in industry for (among other things) stripping paint and rust from automobile body parts! Although the molarity of cola is much lower than that of industrial hot-tank mixes, it's enough for fun. The best part of this method is that it is quite plausibly passed off as an accident! Simply spill a nice warm soda across the car in question. It's best if the day is hot, as well. Leave it there. After some time, the phosphoric acid in your sugared refreshment will begin to remove the paint and primer from the vehicle's surface.

The Cat-Stack Catastrophe This one doesn't really mark the car in question per se. However, it's great fun, and can be used as the 'non-damaging' one in the pack. This works best if the target lives in suburbia and the car doesn't move for a couple of days. Ideally, when the owner's out of town. Fill the hubcap areas with tuna fish. That night, any and all stray cats in the area will decide that that car is juuuust what they want to sleep on...and the owner will return to a stack of felines. If the smell has worn off (after a couple of days) the cats will still be able to smell it, and will follow the car everywhere, to the confusion of the owner.

Safety Tips
I must say that I don't recommend you try these on your neighbor's new Audi or your Dad's vintage Corvette. I myself have only experimented on safely derelict vehicles abandoned by the side of the road. However, these are excellent tools to retain in the arsenal, just in case someone really, really royally pisses you off.