I usually answer back with something off the wall, like "I LOVE unicorns to!". I learned that from my sisters old roommate, but the crazy things she blurted out were real! The only time I ever reacted was this: I was going into work one day on my 98 Zuma. It had a clutch issue at the time and would randomly hang-up at 34mph max. This guy in a newer Honda Accord keeps riding my ass. I look to make sure he's not someone I know goofing around. He see me looking and gets closer. The clutch un-jams and the Zuma gets to its normal 45mph and he's still on my ass. So at the nest intersection the light turns red, I'm going 45 with this guy on my ass and slip down the middle of all the stopped cars. He slams into one and starts a serious chain reaction! By the time I get to the front of the cars the light turns green and I just continue on. He should have been paying attention and not staring at my ass.