If mass combat, or rather: it's opening, counts, then the charge of the Rohirrim:
If we are talking only individual fights, the one I immediately remembered is the table fight scene from Ip Man 2 (the last part, starting roughly at 06:00):
Alley fight scene from "They Live." A knock-down, drag-out WWE style fight over not wanting to wear a pair of glasses. Poor fashion choice? So over the top that I couldn't help but love it.
Mountain vs Red Viper. There is so much build up. Viper voulnteers to champion for Tyrian but has his own motives. The fight seems like justice, but then...
Stunning choreography. Spot-on costuming. Brilliant score.
It's got it all: tension, heroics, pathos, ingenuity, triumph.
I am deeply moved every time.