What a wealth of writing resources are available online! Recently, I've been enjoying Bryn Donovan's blog that includes How To's, Writer Worries (!), and Prompts. In this entry, she provides a long list of prompts - fifty of them! - related to fight scenes. Some of my favorites?
#1: Two people fight without waking or disturbing a third person.
#9: Fortunately, his blood is also a weapon.
#11: Someone's trying not to hurt the person who's attacking him.
#25: Bullying the bartender or server was a mistake.
#37: The fight is a ruse to distract people from what's really going on.
Great practice, so choose your favorite, set the timer and write!