Volitional Wounds

Here I'm going to explain the wounds system I favor in tabletop RPGs and use in Eldritch Gambit and METTLE Core. The idea is that a player chooses for their character to take an injury in exchange for ignoring damage. This can be any amount of damage from a single blow, as long as the character still has HP left. Discretion to use it is entirely left to the player.

For example, Bob the Fighter has 12 HP and suffers 10 HP damage from an orc. Instead of dropping to 2 HP, they can choose to forego the damage and suffer a wound penalty instead. There's not a lot to it other than deciding what a "wound" is in your favorite system. You could even swap in a roll on one of those oft-maligned critical hit tables, which would be well-used in this case.

This idea mutated from the procedural advice given in Eldritch Gambit, which recommends that players should be left to describe injuries and other misfortunes that happen to their character. This was in turn inspired by the etiquette of Dragonball Z internet forums for how members should describe fights between their characters. It will seem familiar to those who know how FATE handles Consequences and Voidheart Symphony handles wounds.

Advantages:

• It is voluntary and does not impose itself on the Players or GM. It is not another thing you have to deal with when the dice tell you.
• It is consistent, working the same for PCs and NPCs. You can expect the GM to use it only rarely and for important NPCs.
• It is an "interesting decision." If you suffer the wound, you get to fight on impaired. If you do not, you remain perilously close to incapacitation or death. The choice is thus between impairment or imperilment.
• It clarifies what HP are in these games - mere flesh wounds or positioning. Serious meat consequences are faced when you lose all HP or take wounds.
• It is adaptable, slotting in easily to just about any game that uses some variant of HP.
  

That's all there is to it.