I'm glad to see Wilmington mentioned on the first page!
I agree with others that Reykjavik is a great city, but I heard so many things about by the time I went this year, it wasn't not what I expected.
Here's some for me:
Newport, RI: I was surprised at the immense amount of history in the city: The Breakers, all the other Gilded Age mansions, the oldest synagogue in the US, the oldest tavern in the US, the old colonial Rhode Island capitol, one of the oldest baseball stadium grandstands in the US, the Tennis Hall of Fame, the birthplace of tennis in the US, and the Naval War College.
Flagstaff, AZ: I knew it had a lot of Route 66 history. It still had more than I expected. It also turned out to be a pretty cool college town. The scenery around town was more majestic than I expected.
Richmond, VA: I thought it was smaller. It is more like a borderline major-league city. It's also like a Northeast city in the South. There's a ton of nice neighborhoods, and the suburbs are also very pleasant. Lots of history in and around the city, as you can imagine.
I could probably come up with more if I really thought about it, but these three come to mind first.