When you take a fatal blow, you die. Unless of course, you say you don't want to. In which case, say what you sacrifice, it has to make sense*. It could be:
- A point in a stat
- A limb or part of a limb
- An unscarred piece of flesh (it's now scarred, duh, and not a cool scar either)
- A bodily function (a non-vital one, but one that's really annoying, like sight or bowel control)
- Dignity/social standing
- Material wealth
- Anything else you can think of
You lose whatever it is, permanently**. If the DM thinks you've paid your dues, you're unconscious and messed up, but no longer bleeding to death. If they don't, repeat the above move, or die.
Optional: You only have one opportunity to bid on your life, and you must sacrifice whatever amount of things you deem expendable.
Optional: The DM doesn't have to tell you if you survived or not until someone tries to resuscitate you.
Optional: Bluffing. Somehow. Figure it out.
*If it doesn't make sense, you lose it, and it does nothing.
**Not really permanently, but at least for two campaign arcs. You nearly died, man.
Thoughts?