Then there's everyone else... I am a super courteous driver (much to the dismay to anyone behind me) and tend to let everyone in (unless it's some jerk who is driving up the shoulder to get ahead of the traffic a bit before they have to cut in- I let them sit). It drives me nuts when there's a TON of rush hour traffic, and I'm nice enough to let some person jump into traffic from a side road, and they give me nothing. I get courtesy waves so rarely that I get truly excited when I get one. Sometimes I'll get one with my brother in the car, and we'll both be like, "Hey! Courtesy wave! Awesome!" How sad is that?
I love courtesy waves, but in terms of priorities, I'd rather at least one hand be on the wheel than get that little wave!