In terms of a wounds system, I'm using the Mutants & Masterminds wounds system, but I added a quasi-gritty element. In the normal system, each stun hit gives you a -1 penalty on future stun damage saves, and each lethal hit gives you a -1 penalty on all future damage saves. In my quasi-gritty element, each stun hit gives you a -1 penalty on all damage saves, and each lethal hit gives you a -1 penalty on every roll of the d20. So if you're beaten to the point of barely being able to stand, you aren't going to be whirlwind attacking terribly well.
I'll be debuting the system with my group soon, and we'll see how it goes. I predict future casualties but a lot more learned caution as people take a couple of hits and then realize that life sort of sucks when you can't swing a sword without wincing because of the slash across your ribs.
EDIT: Also, yeah, as others have said, Conan's system is good, even if you stay with hit points. You could make it even grittier by using the d20 Modern "Massive Damage Threshold = Con score" instead of 20, which is what Conan uses (and on a blown save, you immediately drop to -1 hit points). They have armor as DR, but it's more complex, because finesse weapons (rapiers, daggers, etc) can bypass armor's DR on a really good hit, and strong enough weapons swung by strong enough people can blow through armor to ignore the DR on a good hit -- and damage the armor in the process.
The one thing I can see from Conan's rules is that combat will be slowed down a fair amount. There's more to remember, more numbers are involved, and it's definitely more complex. I believe that this was done on purpose to give numbers-geeks something to focus on in the wake of magic, which, while still present in Conan, is much less of a focal point -- you can have a complete party without a spellcaster, and in fact, if you're a non-evil party, having a spellcaster is often more trouble than it's worth.