OMG! Those pictures are horrible. I was mad with what happened to me (below) tonite. I can't even imagine how much anger you must have right now. When the vehicle gets repainted I would seriously look into a car alarm or some video cameras.
Originally posted by Evolution:
10) Dump a bottle of brake fluid all over the car
Did I miss anything???
I had the brake fluid thing happen tonite, only it was with a squirt gun. The Blazer's occupants sprayed me while at a red light. However guy who ownes the Blazer that sprayed me has his truck up for sale, and I now have his phone number. Phone number = address.

Here are a couple for the list:
1) Go to a movie theatre and drain the icky juices out of the garbage bags in the dumpster. Pour into air vents. This stuff can instantly trigger most peoples gag reflexes.
2) Paintball their vehicle
3) Freeze paintballs and use semi-automatic paintball gun with a silencer in a drive by on their car (or Blazer) in the middle of the night.
4) If vehicle has slotted wheels, pee on their brakes. Short term, but it stinks.
5) Put expandi-foam in the air vents or in the exhaust tip(s). The more you can fit in, the better.
6) When I was younger my dad would go out, once a year and clean my great grandparent's headstones with hydrochloric acid (IIRC). He would wear rubber gloves while doing this. It would take a few hours but the acid would finally munch the gloves. Well, put his stuff in a partially filled balloon. Set the balloons on the vehicle, puncture balloon with a pin (wearing latex gloves the whole time so you don't leave any prints). If you trust the balloon enough, you could throw them from another passing vehicle.
7) If you don't want to damage their vehicle, but you want revenge, and they just so happen to live in an older neighborhood with large trees, do this.

Sneak into their yard in the middle of the night. Use a small drill with a long bit and drill holes into the tree. 45 degrees works well, drill down. Find a small shot needle (the needleless kind you can squirt people with) and fill with Round-Up. Inject this into the tree. Volia, instant tree removal bill that probably won't be covered by their homeowners.