Has to be the one with Lance riding along the ocean, the birds, the Harley's, the buffalo's, etc. I'd love to find that heavily forested hill he's going up in the long version (if it's real). Waving (or shaking his fist) at the kids in the hospital is a great touch!
I've seen the commercial many times, but I still slow down the TiVo to watch and listen to it again. IMHO, it ranks up there with the 1984 Apple commercial