Hoogenband is the only swimmer to have beaten Phelps twice at Olympic Level, Thorpe also did it in the 200m at the 2004 Olympics, in the so called "race of the century" between Thorpe, Phelps and Van Den Hoogenband.

Thorpe is also the only swimmer in olympic history to get a medal in the 100, 200 and 400m events in the same olympics.
Also, bekated thanks for the correction locket. I don't generally follow the rowing.