Traveller, in its "Classic", "Mega" and "Mongoose" incarnations (the only versions I have access to) has an interesting system for tracking wounds. Here are some random thoughts about this system.
Rather than abstract "hitpoints", damage is tracked by reducing your three physical stats (Strength, Dexterity, Endurance) directly. If for example your Dexterity is damaged, you're going to have more trouble firing weapons or doing delicate tasks. The details vary by version, but essentially when you "zero" one stat, you are lightly wounded, when you "zero" two you are seriously wounded and require surgery, and zeroing all three means you're dead. (Death can be averted in some versions by quick application of medical procedures.)
Oddly, animals and vehicles use a different system, where they list the number of points needed to incapacitate, and the number of additional points to kill. They don't worry about "stats".
Classic Traveller is the most straightforward. All damage is in "Hits", where each "hit" is 1d6 points of damage. Armor makes you harder to hit, but if you do successfully attack the target, you roll the Hits of damage immediately, applying each whole dice to a random stat. (We always played that you could choose the stat, because that's more fun.) The first hit in any combat is supposed to come entirely off of one stat, on the theory that your first wound could knock you unconscious. I use that rule for "mooks", but not important characters. For animals, the points all go against their "hit points".
MegaTraveller takes a different approach. You add your physical stats together to get a "lifeforce rating", which indexes a table that gives you an animal-style "incapacitate/kill" hitpoint track. The difference from CT is, these numbers are in "hits" not "damage points". Armor in MT reduces the number of hits (possibly to zero), and only after combat do you take all hits and then apply them to the stats of combatants you care about (usually only PCs). The downside of MT armor is that the rules for penetration are complex and involve a somewhat complicated set of fractions. It's no worse than THAC0 in D&D 2e, but it lacks the immediacy of "roll to hit, roll damage".
Mongoose goes the exact other direction, giving animals physical stats, but specifying that the first hits always come from Endurance. Damage is rolled at the time of attack, and armor blocks damage points. MgT armor seems much less effective than CT and MT armor, but I believe that's a side effect of how they brought the MT armor values over.
I've always found CT's "armor modifies your chance to be hit" to be an odd abstraction. For example, rifles get a big bonus to shoot at unarmored targets, and it's practically impossible not to hit someone at 10 meters with a shotgun. Someone posted a "fix" for this that involves first rolling to hit without armor modifiers, then rolling to hit with ONLY armor modifiers to see if you penetrate. I like this idea a lot, especially since against unarmored opponents, it generally means that you won't need to bother rolling penetration because the hit will be automatic. However, I feel like that system would work better with MT's "track the hits, roll the points later" approach.
T20, being a D20 derivative, has an interesting take on damage. "Hit Points" are renamed to "Stamina", and you always take damage to your Stamina when you are hit. At zero stamina, you pass out, but are not seriously wounded. In addition, you have Constitution worth of "Lifeblood", which you only lose if the damage penetrates your armor or you are unconscious when you take the damage. So in other words, get shot without armor, and you'll probably die, no matter how high level you are. But a veteran is going to be able to keep going a LONG time with some decent armor. I like this system a lot, and it would be interesting to try to graft it on to a more standard version of Traveller.
Something to think about for another entry....