No, you first
I've heard Seattle's peculiar driving etiquette discussed a lot, but I've noticed something interesting and maybe you have, too.
When the driver at the intersection stops and insists that you go first, and you don't play the "you first" game back with them and instead proceed, have you noticed that some of these people will then gun it out into the intersection because you didn't play the wave game with them?
Weird. If they didn't want me to go first, then why all of the formalities?