Boston for the drivers' unpredictability.
The Beltway for obvious reasons.
LA for shear stupidity (I was driving up 91 through MA once and saw, on an otherwise EMPTY road, a wagon going about 50 mph in the far left lane -- 3 lanes to choose from, 65mph zone -- said to passenger "That chick's driving like she's from LA." I got up close and saw a plate frame from some car lot in Santa Monica. Go figure. Brother-in-law told me NOT to step on the brakes, but to coast when slowing to save gas. And that he was taught this in Drivers' Ed.
Uh, sorry, I think I'd like the people behind me to know I was slowing. I've had to teach my husband how to drive properly. Also, I get hounded by his LA family for my "dangerous aggressiveness" but the Boston family ASKS me to drive them around!!
)
NY for its aggressiveness, but I'm used to it and drive like that, too.
New Jersey for the apparent custom of giving those coming INTO the roundabout the right-of-way over those ALREADY IN the roundabout.
The whole NE Corridor for the huge quantity of timid women who don't know how to use exterior mirrors in large SUVs bought by their overprotective husbands.
Haven't driven in Miami. Having read that, I don't plan to.
Really, really like driving in Germany. Only like driving in Italy when I'm well-rested.
edited to add: just remembered the Penn. tpk. Damn that's horrible.