I just went to an outdoor concert in September with the following lineup: Fastball, Tonic, Sugar Ray, and Gin Blossoms. It was an awesome throwback to my high school/college years. The first 3 were previously mentioned in this thread, but I don't think any of them qualify as one-hit wonders. Fastball had a 2nd big song (as mentioned before) and Tonic had at least 2 more that I would call "hits".
During the Gin Blossoms' set, the singer thanked the other bands for touring with them and then mentioned that despite being the headliner, they were the only band of the 4 without a #1 hit in the US. I thought that was interesting.