As some of you may know, there's an optional rule in the DMG where, rather than calculating AC by adding base 10 to all the various modifiers (armor, shield, Dex, etc.), you take those modifiers and add 1d20 each time the character might get hit. In other words, every attack is an opposed roll; 1d20 + attack bonuses versus 1d20 + AC bonuses.
It sounds like it'll slow things down--and it's true that combat took a little bit longer. But we didn't notice. The battle was a lot more dramatic than anything we'd done before. Now, I don't allow my players to describe their attacks as "I swing, I hit, I do X points of damage." I insist on knowing exactly what they're doing--even if it's just telling me what sort of attack they're making. I do the same, now, with the defensive roll--are you dodging, ducking, parrying, leaping backwards, rolling beneath the claw, etc.
And it worked. The fact that the players now had an action to describe in both stages of combat (as did I, of course; I hold myself to the same descriptive standards) made the combat really flow. They were able to base the description of their attack this round off their defense last round. (In other words, they ducked last round, so this round they describe their attack as an uppercut from a crouch; that sort of thing.)
I realize I'm repeating myself, but I have to say again that this was the most dynamic D&D combat I have seen in years. I guess I'm just excited because, as long as I've been playing, I figured there wasn't much new we could do, rules-wise, to add to the fun. I was wrong.
Have any of you ever tried this rule? And if not, I strongly suggest you give it a try. Yes, as I said, the fights may take a bit longer (though not much, once you get used to it), but the're far more satisfying; they may take longer, but they move faster.