One of the worst ways for a GM to do in a PC during the course of an adventure is by means of some kind of instant kill. This most often takes the form of a trap, like the ones in the various Grimtooh's Traps books. (I can't think of a time this ever happened to one of my PCs, which is just as well because I probably would have made a scene.) But there are times when PCs face certain death. The ancient tower collapses around their heads, or the starship's hull is breached and they're blown out into space. Assuming script immunity isn't an option, what do you do then?
Some games have a special mechanic. I think it was TSR's Top Secret that gave each PC a (secret) limited number of Fate points that they could use to cheat death. Once your points were gone, well tough luck. CORPS has a similar mechanic with its ASPs, or "Ass Saver Points". So that's one method. Give your PCs a special pool of points the can expend to save their necks when all else fails.
Another method is that the PCs make some sort of very difficult saving throw. For example, in V&V if your character is in a situation they shouldn't be able to survive they can make a saving roll of 1d100 against their current Power to see if they miraculously survive. Mike Stackpole's Mercenaries, Spies & Private Eyes has something similar with its Megadeath Luck Saving Roll. The idea is that if the PCs want to perform some kind of death defying stunt, and presumable also if the want to cheat death, they have to make an appropriately high Luck saving throw.
Both of these are good systems. I like the idea of tough saving throws more than special points, but either way would work. In any case I think there should be a way for characters to cheat death. Is there another way to handle this that I'm missing? Do you think one way works better than another? Which method do you use in your games?