Giles lists a few icons that he likes (Notational Velocity,Spotlaser) but he admits that he is no designer. He turned to John Hicks (designer of FireFox's icon) and Jasper Hauser (creator of Camino's icon) to give their opinions about icons and list a few of their favorites.
I have always had a soft spot for the Finder icon, though I suppose that one is fairly obvious. How about you? Fire off a comment letting us know what icons you like the best.