No love for the final sword fight in Rob Roy? Still the gold standard for realism IMO.
I also really enjoyed the final fight between Obi Wan and Darth Maul. In particular the one sequence where Obi Wan storms in and blocks Darth Maul’s light saber over his head and behind his back. (3:49 here).
Beck (The Rock) vs. Ernie Reyes, Jr. in the Rundown. Very awesome. Course, most of the action in that film was pretty sweet.
Oh, and Spider-man vs. the Goblin at the end of the first film. Just brutal.
The Patricia Arquette vs. James Gandolfini scene in True Romance.
The Dread Pirate Roberts Vs. Inigo Montoya.
The opening sequence fight in the new Casino Royale is pretty good. The James Bond of the books is supposed to be a Judo expert, and when Bond is dragging the contact to drown him in the sink he appears to be using a sliding or thrusting collar choke. Good stuff.
Sauron stole mine. 
I agree that the shower fight in Eastern Promises was … something else. Very realistic and brutal. I was cringing and shaking my head the whole time.
And speaking of Firefly, I love both iterations of Mal vs. the Agent.
OH! And ya gotta love the school hallway fight in Gross Pointe Blank!