For sheer entertaining comedy you've got to love Darcy vs Cleaver in Bridget Jones's Diary. I mean, that's basically a slightly exaggerated version of every real fight between sober people I've ever seen, right there.
A slightly different take on comedy fight scene, Indiana Jones vs The Unfortunate Egyptian Swordsman. Various apocryphal stories tell us what, in particular, was supposed to be wrong with him, but the fight choreography tells us for a fact that there was supposed to be a vicious punchup there but Harrison Ford felt too diseased/food poisoned/tired/tortured by raging hemorrhoids to do the scene. And you know what? The punchup just wouldn't have been as cool.
For a serious fight scenes, well, how about two [http://www.youtube.com/watch?v=tj_089srvis]. There's plenty of hyperkinetic modern fight scenes that aren't fit to wipe the blood streaked sweat off the nipples of those two.