I came up with this awhile ago because I wanted a D&D / Pathfinder rule to emulate the way that fiction characters often are defeated with a disarm and a throw instead of suffering a fatal blow.

Using these rules to take someone alive is difficult, and may give them more opportunities to keep fighting if you fail. Imagine fighting a dangerous person that is clobbering your group. Instead of killing him, you try to knock him out and fail. Someone might yell, "Stop messing around and finish it!"

This rule can be used to replace the subdual damage system.

Only the original hit points gained at first level represent actual health and injury. All additional hit points and related damage represent near misses, painful superficial injuries, and manageable cuts and bruises. Only the final strike represents a life threatening injury.

So a character with 100 hit points that suffers 90 damage from 3 hits has probably been shaken to his core, but he isn't actually, bleeding from an injury.

Note: These aren't restrictions, just more options.

The character that delivers the final strike has a few options under this house rule:

1) Deal Normal Damage and Attempt to Kill the Opponent.

For this, there is no change to the rules.

2) Disarm and Knock Prone

The attacker can choose to automatically disarm his opponent and knock him to the ground. This is technically more difficult than simply killing the target and as a chance for failure. The victim gets to make a reflex saving throw with a DC equal to 10 + 1/2 the attacker's total level + his Strength bonus. If he makes the save, the attack is considered a miss, though he may realize that his enemy isn't trying to kill him.

3) Knock Unconscious

Instead of dealing a lethal blow, the attacker can attempt to incapacitate his enemy. His enemy makes a Fortitude saving throw with a DC equal to 10 + 1/2 the attacker's total level + his Strength bonus. If the Fortitude save is successful, he is still "Staggered." If he fails by five or less, he is "Stunned." If he fails by more than five, he is knocked out and rendered, "Helpless."