I have a friend, who many years ago came up with this idea.
For $50, you go to the police department and purchase 3 special darts. Instead of having a sharp pointy end, it has a bulb with a special adhesive, which only the police have the solvent to.
In your travels, if you see someone being a jerk-off, you hit his car with a dart. It is now a flag to him and others to watch this guy. He then has to go to the police department and pay a hefty fine to remove your dart from his car.
Just to add insult to injury, after the third dart is removed, you're given a $15 ticket for being an idiot.