See I give the Stare and then the shaking of the head and then the rolling down of the window...and then the stare again...oh and the Italian hand...I throw that in also....
Ahhhh, a fellow road-rager... Sometimes the finger goes up, but not usually for littering...
OK, side note...locally about a year ago the police dept specifically said they were going to crack down on this very act, littering cig butts...I never heard anything beyond the initial PSA but I wondered how many they nabbed that are so used to tossing 'em, they don't really even realize what they're doing...