Here in LA I see a LOT of Porsche's so its hard to wave at each one, but I always make eye contact and give a thumbs up from my 911SC.
One day, I had a guy in a 997 GT-3 pull up next to me at a traffic light, he rolled down the window and said, "Damn, I should have bought an air-cooled car!".
Same thing happened up in Silicon Valley last month when I see a 991 slicing through traffic from behind to catch up. At the traffic light, the female passenger rolls down the window and while pointing to the male driver, she says, "I told him to buy an air cooled car but he wouldn't listen!".
People generally crack me up!