I don't flip people off, but I do yell obsenities at them. People suck at driving. Half the people that drive should never have been allowed to get a license.
I want a car that gives evil looks at other cars. Winking could be cool too. Why the hell would you want your car to laugh though? It would see someone like run into a pole and it would just bust out laughing.
In Japan they have a car that's like a mood ring. It's antenna wags when your happy, and the lights change with how your feeling, when you're sad it will play your favorite song because your steering wheel can does something to tell it who you are. It's v. strange.