Seattle drivers
I know that bad drivers aren't anything that is unique only in Seattle, but Seattle drivers are horrible in their own passive aggressive way.
First off, everybody enjoys driving a good 10 miles under the speed limit, especially when there is a slight drizzle. I'll be driving down the freeway with a maximum of 10 cars in sight and all of them are doing 50 in a 60. You'd think that in a place where it rains as much as here, people would know how to drive in the rain.
Driving in the snow is even worse. Seattle people love pointing out the fact that it doesn't snow in Seattle very often. It's a matter of some kind of city pride to them. The reality is that it snows here every single winter. It doesn't always stick and it doesn't always stick around very long, but it snows every winter. And yet nobody knows how to properly drive in the snow. If you don't believe me, go to youtube and search for seattle snow drivers. It's like watching bumper cars.
Also, why does northbound I-5 drop down to two lanes through the MIDDLE OF DOWNTOWN SEATTLE? Downtown traffic is bottlenecked even in the evening and very early morning hours. And all because somebody decided to build the convention center on top of the freeway.