While reading Dragon issue #118 I ran across two articles for adding systems in Advanced Dungeons and Dragons that Hackmaster has as part of it's core rules.One article on Pain ("ARRRGH!!!"), and another on Hero Points ("A Hero's Reward").
Dungeons and Dragons has always had an abstract hit point system. It was added to the earliest versions as an enhancement to the chainmail rules way to prevent the characters from dying instantly. People got attached to their characters, and this was a way to allow them greater survivability. This abstraction is very 'gamey'. There are no long term consequences for damage. In the older versions, the primary nod to actual damage was the rest required after being dropped below 0 hit points.
This is a great thing in the context of people playing a game. Who wants to roleplay walking around in a cast for six months. Over the years, more than one or two people has said - this is entirely unrealistic (by which they mean, it's destroying their suspension of disbelief)
The article uses a system of "cumulative wound tracking" with a variety of "wound location charts" each containing penalties for future actions. This means as you get closer to death you are less and less effective in combat (versus the default system where you are 100% until you're out). These wounds are abstract, not tied to a location. There is an 'advanced' variant where the wounds can be on a particular limb, providing more specific penalties.
This system is exceedingly complicated requiring tracking of every individual wound greater then a percentage of hit points based off your race, class and constitution. There are half a dozen matrices in the article giving those percentages. Most of the percentages are between 18%-21%. At the levels of hit points that old school characters have these small fluctuations will hardly ever make any difference in the sizes of the wounds.
Hackmaster characters have a lot more hit points than normal Dungeons and Dragons Characters (the 20+ hp kicker). I've been exceedingly impressed with it's system for critical/pain/called shots. It overcomes the obvious issues with extended grindfests due to high hit point totals by having a "Threshold of Pain". Every time you take damage in a melee round equal to 1/2 or more your starting hit point total, you must make a saving throw versus death or fall to the ground incapacitated by pain. This speeds things up greatly and helps maintain that suspension of disbelief. Another unforeseen benefit to this system is that often after a fight, many of the participants are still alive, although possibly in shock and on the way to death.
As far as individual wounds, Hackmaster works just like the earlier abstract models, unless you're dealing with criticals, which can cause specific wounds to bones, internal organs, or muscles. This system is also complicated, ignored for the most part on the monsters (where the bonus damage is what's important). But for the players, the benefit is that they can sustain long term consequences from their battle. I've found that this avoids being overbearing, because it has to be a fairly severe critical hit on a vulnerable location before these things come into play. I can think of maybe 20 or so wounds over the course of nearly 2 years of play where this became a factor.
It is totally possible in old school play to just arbitrary describe wounds based off damage done, but I find that a table like the Hackmaster critical table prevents Dungeon Master bias as well as enhancing creativity. ("Wow, I hit him in the eye again!")
I also have to say that I'm a big fan of the called shot system in Hackmaster. It's often very difficult to prevent called shots from being strictly better or worse then normal attacks, and I think it does a very good job of riding that line. There are differing penalties for the sizes of body parts on differing sizes of creatures applied to the roll (1 chart). You critical on a 19-20 instead of a 20. There is another table for the 'armor coverage' of different armor types (1 chart). There is a third page showing how much damage each body part can sustain before it becomes disabled (1 reference picture). It makes them a useful tool that can achieve a specific effect at a consequence. You normally only need two of the pages, and I have them together for when it comes up in a game. A little extra reference, but by no means overwhelming.
The hero point article is fairly simple. Players get points equal to their level every day which they can use to alter rolls by +/-1 per point. On a first read, this seemed extremely broken to me for several reasons, as well as missing one of the core issues of these types of systems.
The whole idea behind hero/action points is that players should have some meta-control over the game. This is a good solid principle. A group of people are getting together to play a game, it's only reasonable that they should have some say in what happens in that game - action/hero points are a mechanical way of having that happen. There are a lot of random die rolls in a game, and allowing the players to mitigate some of that randomness is a very modern idea, but in play is very useful. If you're playing in a game with save or die, and the party is middle to high level, having an in game system for hero points and mulligans is fun for the players, since failing often turns into just a gold tax. I don't feel it's specifically opposed to the principles of old school play.
Again, I like the Hackmaster system better. They have honor, which you can spend to add your honor die to rolls (which changes based on your level). Characters in great honor get +1 to all rolls, one mulligan a session, and bonus experience and reduced leveling costs. You may also purge your honor (spending it all) to avoid any one in game event, but this can put you in bad karma, locking you into low honor, unable to advance.
There are some problems with it also. Points are given based off a large series of actions in the context of player alignments. The system allows a large degree of wiggle room and DM fiat (40 points +/- per PC per 'adventure' when most table awards are 1-4 per action), but if I'm assigning honor based off my own whims, it may not be nearly as consistent as what the table suggests. So I spend a long time (~3 hours) dealing with experience and honor after each game session.
Why don't I just handwave it and hand out what I think is close? I'm certain I'd be close to the table most of the time. If I just handed honor or experience out, eventually I'd just be deciding the pace of the game. Maybe there's nothing wrong with that you say? In the context of old school play, there is. Regardless of what they do, their actions don't matter because the pace is being set by me instead of by them. So yes, it takes some additional time to go down the list of honor awards for every PC and total up all the experience. But the end result of having players know that when they reached level eight after 15 months that they earned it, every last experience point, and that there was no guarantee that they would survive that long is of far greater benefit then the time I spend calculating these values.