I must second the X2 fight scene, I wouldn't have called it a fight though....
I really liked the fight at the end of TPB, "My name is Inigo Montano, you killed my father; Prepare to die.". But that might come under best line, or best then scene then a real fight....
There are some fight scenes I really enjoyed, but I can't rememberr the name of any of then. Both are from martial arts movies, the first is a fight scene in a circus (I think) on stilts. It was amazing, flips, kicks the lot, but on stilts! The other is in a towl lined with shadows and white sheets, the enevitable happens andthey play the hiding game. One in white the other in black.
Samurai jack has loads of brilliant scenes, I can't mention just the one though.