Yeah pretty pathetic, I had my old EF egged once as i drove past a group of guys on the street. What they didnt count on was me doing a Uturn, coming back and landing about 30 eggs on them - had a carful of mates and we were on our way to egg somebody elses car
:.
The paint thinners one is a good payback but if you spill it in your car you'll know about it. Its really not worth doing because if it does stuff their paintwork (which it will) and anybody sees you etc etc, you're gone.
If you do want to get them back (I would), stick to eggs or something that can wash off. I know it sounds weak but the last thing you wanna do is provoke these guys to attack you and your car with something a bit stronger than water.