Critical Hits, Weapon Types and Wounds

CRITICAL HITS, DYING, GETTING WOUNDED

If a player or GM rolls exceedingly well to hit, the attack is a Critical Hit (as adjudicated by your particular rules, but I like a 5-10% chance for most characters, maybe higher for certain monsters). 

Critical Hits are a big deal, so tell everyone at the table when you roll one and tell the GM what weapon you're using, if it's not already clear. 

Some Critical Hits Cause Damage or Debilitate the Target

Being subject to a critical hit from ...

Smaller bladed weapons  (daggers, short swords, stilettos, punch knives, claws, icepicks), and Claw and Bite attacks from normal or small enemies are Frenzied Stabbing/Biting/Clawing attacks (attacker rolls damage as normal, but adds an additional damage die* to the roll as it stabs/bites/claws like a maniac); and

Whips and the like Trip Up the victim (victim falls over, spins around, stumbles, is disoriented, can't move its next turn, is pulled towards the attacker; if attacker is player-controlled, player describes how this might happen and GM determines if it is so or happens differently);

Some Critical Hits Cause Wounds

Being subject to a Critical Hit from certain weapons earns you a Wound. There are Wounds, and then there are also Crushing Wounds and Hideous Wounds which are just special types of Wounds. If you want, just delete "Hideous" and "Crushing" from the below. I like the granularity, but that's me.

Critical hits with...

Edged/Piercing/Slashing/Claw/Bite attacks cause Hideous Wounds;
Bludgeoning/Crushing/Fist attacks cause Crushing Wounds;
Claws, Bites and Most other melee attacks from very large (think dragon, dinosaur, etc) creatures cause two Wounds and are therefore insta-death;

Flails, Maces and the like cause Crushing Wounds;

Lances are awkward to use on foot but as a mounted attack can cause Crushing Wounds.

Dying

Hitting or passing 0 hp means you're dying. Save or die. Successfully saving earns you a Wound and however much HP would bring you to 1 HP.

An Otherwise Lethal Situation
Getting hit by a very large dragon's bite attack, a giant's club, fallking rocks, lava, potent acid are all save or die situations. Succesfully saving means you've made it but with a Wound.

WOUNDS

So it didn't kill you, but you're all messed up: you've got a Wound. You've either got a Wound from a Critical Hit or from nearly dying. In either case, before describing the affects of the hit, the GM should roll a d6 and consult the below to determine Wound location.

Wound is to...

1-2 Torso

3-4 Arms

5 Legs

6 Head

With the above adjusted to account for target, attacker size and the general logic of the situation. (Like: the likelihood of Arms and Legs are switched if the attacker is really small or the target is really tall and even bigger discrepancies increasing the likelihood of Wounds to one area or another correspondingly)

Wounds are terrible, horrific, debilitating, scarring injuries. They require care and attention right away and then again in the coming weeks lest they become fatal.

If Wounded, your max hp is immediately decreased by 50%. Two Wounds mean automatic death, no save. You can't heal hp beyond your max hp and any HP currently beyond the max is lost.

Wounds take a long time to heal "naturally" (I use three weeks, but whatever is sufficiently long to last beyond the current session).  Every week (or every third of the chosen healing time) make a save v poison. Fail once and you're infected. Fail twice and you're diseased. Fail three times and you're dead, no other save. Ambient grossness affects Wounds too. So, wading through a swamp with a huge gash down your thigh is probably going to lead to some bad stuff (likely you get an automatic fail for that week's save). Bed rest and light activity will help you along nicely, and medical attention might get you an automatic save. Resting in town, unthreatened, with occasional medical attention is almost certainly an automatic save.

If a Wound is Hideous it leaves a horrendous mark, no matter what. You're losing a chunk of flesh, a nose, an eye, a hand. Player should consider how the Wound was earned and then suggest what's been lost. Hideous Wounds have to be bound and cleaned regularly or you fail your week's save. Hideous Wounds also bleed quite a bit and need to be treated (bandaged, bound, whatever) or else the PC takes d6 damage each round following receipt of the Wound until treated.

If a Wound is Crushing you've broken some bones. The affected area is totally ruined until you heal it, get it set. If it's a leg, no moving other than an achingly slow hobble until it's set (and then, you're still slow); it it's an arm, you can't use it for anything, set or not. If it's your head, you're dead, no saves to recuperate. Crushing Wounds have to be set and cleaned or you fail your week's save.

RATIONALE

Part of the reason I posted this was because +Joey Lindsey shared a really intriguing way of seeing/managing hit points that I want to try next and I wanted to have this posted, with a pin in it, while I play around with Joey's HP system.

Full disclosure: the idea of "Wounds" and certain mechanics associated with them are pretty much taken whole cloth from +Trent B's awesome New Feierland house rules.

Ultimately, the concept I'm struggling with is how to handle PC death. We like lethal games, but there is an interesting middle ground between death and might-as-well-be-dead where the player is now less interested in getting cool stuff and XP for their character and more interested in just making sure that the character stays alive/keeps whatever stuff/XP they've got.

Wounds and the "packs and pouches" inventory management system (here is part one, here is part two) are both ways of shifting the game between the "clever adventurers" mode and the "get to the chopper" mode. The pool/bench system is useful for managing this on the backend, once the (remains of) the party has made it back alive.

*I do something slightly different than OD&D for damage die, but straight d6 for everything works too.

[EDITED 5/24 to add "An otherwise lethal situation"]