The Midnight Sun Chronicles
A d20 Modern hero takes nonlethal damage from non-lethal attacks. If the amount of nonlethal damage inflicted on a character ever equals his current hit points total, he is staggered. If the amount of nonlethal damage exceeds his current hit points total, he falls unconscious until the damage is healed. However, if a single attack deals more nonlethal damage than his current Massive Damage Threshold, he must make a DC 15 Fortitude save or be knocked out for 1d4 +1 rounds (or until healed). Nonlethal damage naturally heals at the rate of 1 point per hour. Magical healing or healing from Treat Injury also heals an equal amount of nonlethal damage.