Was that driver in an SUV? That would make the sterotype complete.

I know a group of riders in Queens that carry a couple of stones with them for exactly that purpose. They never give the driver the finger, etc., they just fling a stone and give them a little dent. I wouldn't advocate this - it's way to dangerous with peds and kids.

Central Park needs to be closed to vehicles. Period. There are enough ways to get to Tavern on the Green by Carriage, etc.