Sparrow Vs Barbosa in the treasure cave. I suppose I was won over by how well the skeletons moved and the music more than the stunt work itself though.
Oh, and Vader Vs Luke in ESB (I've mentioned this somewhere before...).
Least favourite fights are the burly brawl in Matrix Reloaded and Yoda Vs Dooku. The burly brawl had potential to be a true classic but the action was constantly inturrupted by slo-mo, which I think was added simply for the sake of it (and to show off their special effects). In the first Matrix, the slo-mo was used to show off the moves and the incredible powers that Morpheus and Co. had, and watching Smith punch through a concrete pillar was good too
Yoda Vs Dooku was just naff. Infact, Dooku Vs anyone who took him on was naff. I didn't notice any difference between the way that Obi Wan and Anakin fought (except the fact that Anakin had 2 sabres), but in some
incredibly lame attempt at showing off Anakins strength, old Chris was made to look a little out of breath after fighting Anakin, whereas after beating Obi Wan he was a cocky git. Then Yoda came along and all hell broke loose. I know that Jedi's have an uncanny ability to jump very high and very far, but I didn't know they could defy gravity by hovering in mid air, yet Yoda seemed to prove that they could
I need to get out more...