If your mark gets a lot of parking tickets, here’s a little extra refinement you might want to use on him or her. Remove the ticket from the car before the mark sees it. Use one of those novelty rubber stamps that features an upraised middle finger to stamp a message on the ticket, then return the mark’s ticket to the police.
If you don’t have such a stamp, then print or type some foul message insulting to the police on the ticket. Or draw something on it. Blow your nose on it. Or glue an obscene or other appropriate piece of artwork to the ticket before sending it back. Never include any money, of course.