Rolemaster uses a range of consequences of harm: temporary debuffs (eg stunned, knocked down), long term debuffs (eg broken rib, shattered collar bone) many of which bring a degree of penalty with them, and what it calls concussion hit loss which is numerical (like hp) and corresponds to bruising, (mostly non-fatal) blood loss and (to a degree) fatigue. Unconsciousness can be from dropping to zero concussion hits, or from suffering an unconscious debuff result. Similarly, there are two ways to die from physical punishment: either a death debuff (the most serious debuff of all!) or if concussion hits are reduced to a fairly large negative number and then a certain amount of time passes (which roughly corresponds to death from blood loss and trauma due to serious physical beating). Healing rules - both for non-magical and magical healing - are pretty intricate to correspond to this intricacy of the harm rules.
Runequest is less baroque than RM but also has both "unallocated" damage (equivalent to hit points, which can lead to unconsciousness or death) and allocated damage (via a hit location system) which can lead to maiming, unconsciousness (if the hit location is the head) or death (if a vulnerable location is hit hard enough).
In passing, I think part of the appeal of 4e D&D to RM players (whom I played it with) is that its tendency towards "damage + effect" on a hit corresponds somewhat to the RM combo of concussion hit loss + debuffs.
In core RM the harm system applies primarily to physical harm and is also used for some forms of magically inflicted harm. But with supplements it can also extend to mental harm - using the Depression crit table, and giving results (again either temporary or long-term debuffs) that reflect mental shock and trauma. At our table players would from time-to-time call for a Depression crit either for their own PC, or someone else's, when they thought some shocking event or revelation might take its emotional toll. I don't think RQ has anything comparable to this.
Classic Traveller applies damage in points similar to D&D, but it is deducted from physical stats. The first lot of damage taken in a given fight is assigned randomly, and so has a good chance of knocking a character unconscious (especially if a lucky damage roll ens up being allocated to a low physical stat - one stat at zero = unconscious). Subsequent wounds are allocated to stats as the player chooses, in bundles of dice (because all damage is rolled on d6s). This provides some interesting choices, because by careful spreading of damage a player can keep his/her PC up - but then runs the risk of having to allocate (say) 4 points of damage when all three stats are reduced to 1 - which would then be triple zero = dead. Whereas if you allocate the damage so as to take yourself out sooner, you maybe less likely to suffer more wounds and hence only end up unconscious.
In the original printing it was not clear whether reduction to physical stats take effect immediately; but at our table we use the rules from the revised (1981) printing which say that the reductions don't take effect in the combat in which they're suffered - ie adrenaline carries you through!
In Classic Traveller there are PC-applicable morale rules but nothing else for mental/emotional harm.
Prince Valiant doesn't have a separate "damage" mechanic - rather, harm (which can be physical or mental/emotional) is applied directly to the relevant dice pool based on degree of failure of the relevant check. This can create quite a strong death spiral effect, although at our table we have seen a number of unexpected rallies. Typical dice pools in a joust between knights might be 8 to 15; so margins of failure can be fairly big but it's rare for the whole pool to be knocked out in one go. If the pool is reduced to the size of the base stat (Brawn or Presence) or less - and typical values for these are 2 to 5 - then recovery may take time beyond just the conflict/scene at hand, depending on the GM's discretion. And some checks - eg archery - can result in direct reduction to the base stat rather than having to work through the whole pool (which for a knight on the physical side of things typically includes arms, armour and maybe steed). It's a very versatile system because it can do everything from a joust to a debate to a rivalry over a loved one using the same framework and the same mechanical approach to harm.
Marvel Heroic/Cortex+ Heroic has three damage tracks - physical, emotional and mental. A successful action delivers an effect which is based on the size of the die in the pool allocated for that purpose (not the result showing - so eg if your pool includes a d10 and a d12 and the first rolls 9 and the second 2 then you will include the 9 in your total to see if you win, and then use the second - ie the d12 - as your effect because only the die size and not the actual pips matter). When an effect is allocated to "damage" - called stress - then if there is already stress of that die size or bigger it steps up, whereas if it is lower than the new size replaces it. One consequence of this is that it can be rational to spend an action or two building up your pool (in the fiction, this might be improving positioning, have a friend lend you a useful item, etc) to give the chance to inflict a big die of stress in one might wallop; whereas in a pure attrition system it is often not worthwhile engaging in that sort of prep because it uses up turns in the action economy without actually depleting the hit points or whatever that need to be deleted to win. If stress goes beyond d12 then the character normally is hors de combat and any further stress inflicted counts as trauma, which has much the same mechanical effect but is harder to relieve.
Stress isn't the only possible effect in this system. As well as self- and ally buffs there can be various sorts of debuffs (with a variety of meanings in the fiction, from scene effects to disarming someone) but one important category is complications, which mechanically work like stress but have descriptors attached to them a bit like aspects in Fate.
It's a fun system although I can imagine that some tables might find both a mental track and an emotional track (the first is for confusion, the second for fear and rage) a bit much.
The final system I'l outline is Burning Wheel. Each character and creature has a "physical tolerances" scale (based on physical stats plus applicable traits - a bit like feats or race and class abilities in d20 games), with a number that corresponds to Superficial, Light, Midi, Severe, Traumatic and Mortal Wounds. For a reasonably buff fighter typical ratings might be Su 4, Li 7, Mi 9, Se 10, Tr 11, MW 12. For a real weakling they might be Su 2, Li 4, Mi 5, Se 6, Tr 7, MW 8.
Successful attacks generate a damage rating based on degree of success; and that rating then converts to a number (normally between 1 and 15, with 3 to 6 being pretty typical for a hit from a knife or spear but 8s and 10s being well within the realm of possibility. This is then applied to the physical tolerances to work out the injury suffered - so an 8 would be a Mortal Wound for the weakling but only a Light wound for the buff fighter. Wounds themselves are numerical debuffs, which are also associated with a particular location (via the hit location/armour rules), until we get to MW which is - as the name suggests - the death mechanic. If the sum of the wound penalties is greater than the lowest stat then the character/creature falls unconscious, but there is no death result until MW is reached - so it's different from RM and RQ in this respect, though there are rules whereby untreated Severe and Traumatic wounds can "bleed out" to mortal.
There is no parallel system for mental harm in BW, but there is a Steel mechanic which is a bit like a more wide-ranging morale system (applicable very much to PCs as well as NPCs). And some characters (in virtue of race or other traits) have emotional attributes. Sometimes when these grow that can be a sign of progess (eg a priest's Faith). But sometimes not (eg a dwarf's Greed, an elf's Grief or an orc's Hate). When an emotional attribute reaches 10 (which is the max for stats and skills in this system) then the character leaves play - probably ascended to Heaven if Faith reaches 10, whereas perhaps having cast him-/herself over a cliff or into a fiery pit, like some of the sons of Feanor, if it is Grief that reaches 10.
A long post, sorry, but I think it's good to look at some of the very different systems out there. Hit points are by no means the only or most obvious way to go!
