Insulting parking cards
Road rage vendetta
Some people park like there are no other cars around.
We have all tried that the only available parking space is still not available because some retard has parked nearly sideways, so there is no room for your car.
In such a case, one would like to do something terrible to their car. Fortunately, few of us do that, even though we are annoyed.
If you still want to make them aware of how rotten they park, you can put this card in their windshield. As a bonus, they may even think they received a parking ticket.