That being said, I do like to have consequences for more 'gritty' games, less heroic enterprises, such as my Cthulhu Mythos game, my Victorian game, and other genres/settings I tend to prefer. If a character survives near death injuries this adds a bit of 'realism' and definitely adds flavor to the PC, making it a very memorable event. Events with tangible consequences frequently are memorable, like an old scar you have a great story (or a great set of lies and exaggerations) about.
When a player character is brought to negative hp and manages to survive:
Saving throw (paralysis) is made with a penalty equal to the negative hp value. IF failed the character gains one disability.
If a limb takes 10 hp (or half of total character hp, whichever is lower) a Saving throw with a penalty of the hp damage is made. If failed the limb is maimed or amputated (if the fail was by more than 5 points.)
See below for a few suggestions.
Unless you decide otherwise these disabilities only apply when natural healing, instead of magical, is used to heal the hp damage.
Figure out where the disabilitating wound is and apply.
Off-hand penalties if primary hand is lost. No use of bows or two-handed weapos.
The off-hand penalty may be reduced or go away with enough time and practice.
Partially deaf, +1 to be surprised (hearing)
-2 to ranged attacks, +1 to be surprised (visual)
-1 to Charisma checks
-4 to Constitution score, possible hit point loss
Half movement (2/3 with prosthetic)
Difficulty with speech.
-1 to Charisma score
-2 to Charisma score
-4 to Strength score