Ok, after the Epic Destinies post, here is another rule from D&D 4th Edition that I believe also works fine in Pathfinder (or D&D 3.5). It was originally part of a 4th Edition preview article at Wizards of the Coast. I’m posting only the D&D 3.5 portion of that text. It is a simple but very funny rule, as it introduces some randomness and tension without increasing the game’s lethality (actually, it decreases).
Without further delay…
Death & Dying (original text)
If you want to try out a version of this system in your current game, try the following house rule. It’s not quite the 4th Edition system, but it should give you an idea of how it’ll feel.
1) At 0 hp or less, you fall unconscious and are dying.
Any damage dealt to a dying character is applied normally, and might kill him if it reduces his hit points far enough (see #2).
2) Characters die when their negative hit point total reaches -10 or one-quarter of their full normal hit points, whichever is a larger value.
This is less than a 4th Edition character would have, but each monster attack is dealing a smaller fraction of the character’s total hit points, so it should be reasonable. If it feels too small, increase it to one-third full normal hit points and try again.
3) If you’re dying at the end of your turn, roll 1d20.
Lower than 10: You get worse. If you get this result three times before you are healed or stabilized (as per the Heal skill), you die.
10-19: No change.
20: You get better! You wake up with hit points equal to one-quarter your full normal hit points.
4) If a character with negative hit points receives healing, he returns to 0 hp before any healing is applied.
In other words, he’ll wake up again with hit points equal to the healing provided by the effect—a cure light wounds spell for 7 hp will bring any dying character back to 7 hp, no matter what his negative hit point total had reached.)
5) A dying character who’s been stabilized (via the Heal skill) doesn’t roll a d20 at the end of his turn unless he takes more damage.