I used to work in an office building with an attached parking structure that was open to the public. On many days, especially in winter, when the lot was too full, people would sometimes park right in front of the door to the elevator entrance. It became my habit that anytime I stepped out of that door, and into a car, I would take their windshield wipers, and toss 'em in the trash. Eventually, people stopped parking there. tee-hee! I have still adopted this rule in malls and movie theatre lots, too. Park like a douche, lose yer wipers!
I don't encourage this behaviour...but sometimes ya just gotta teach people!