I travel for a living as a self-employed corporate trainer/seminar conductor. I've been all over the U.S. including Hawaii and Alaska. Also been to other countries for work as well as vacation (using those frequent flyer miles).
Outside of U.S.
Canada, Quebec
London (twice)
Paris
Venice (3 times - it gets my vote for "favorite" simply because no traffic, no rush, just sit in St. Mark's Square all evening and enjoy the $14 cups of coffee and listen to the three orchestras take turns playing)
Pisa
Florence
Rome
Switzerland
Mexico, Cancun & Cozumel
In every town (US or Foreign) that I visit, I always try to visit and stay in the area that the locals stay in. Eat at the little local places and try the local cuisine and shop the boutiques. I NEVER go to the mall or eat at the chain restaurants. In foreign countries you can't really experience the local flavor if you don't get out of the tourist areas. I'm always amazed, when visiting foreign countries, at the number of Americans that are packed in the McDonalds.