http://www.crayola.com/store/showdetl.cfm?&User_ID=7609437&St=8647&St2=-89868089&St3=60198077&DS_ID=3&Product_ID=529&DID=6
I got some and have used them on several occasions to leave people a message that park like selfish a-holes. Great invention. I got mine on sale for like 80 cents. But even at 4.99 I think it is worth it. The possabilities are endless with these!!! HAve fun

Note if you can't find these the "gel FX" markers work just as well

My girlfriend is an art student, she has those for other stupid uses, lol. Maybe I'll steal a few for writing on cars

Oh, my god! I need some of those. Seriously...

although sound in theory,
might result in injuries if implemented in certain geographic locations.

Yeah, just do it as you are leaving and try not to get caught

ok, check.