In order:
Mexico City, Mexico
Atlanta, GA
Los Angeles, CA
Rome, Italy
Washignton DC
London, England
Paris, France
Houston, TX
Naples, Italy
Mexico City? If your staying in one area, your fine. If you have to drive to the outskirts or in certain areas, it's the biggest damn mess of cars and bikes that I've ever seen.
Atlanta is driving Hell. Rush hour on 285 is enough to make me want to strangle myself. LA is definitely up there, but I've had worse experiences in other places (maybe because I usually stay within OC most of the time); I guess it all depends on where you are coming from and going to.
I've given up driving in most of Europe, unless I'm heading straight to the countryside. Most cities are just jam-packed with cars and NOWHERE to park, and boy do I EVER mean nowhere.
