each other. (you never said the vehicle had to be moving!)
picking their nose .... saw some ugly broad two knuckles deep yesterday.....thought she was going to bruise her brain....didn't want to know what she did with the booger.
I'd say talking on the cell and texting are the biggest 2 and females primping in the mirror is #3.....here in NY it's against the law to use anything but a hands free phone but it's not enforced the way it should be....