Ok, so I've said before that I don't like killing PCs. I'm going to talk about that, but first I want to talk about and reiterate some reasons why.
The first thing to consider is that this reluctance only extends to long running PCs. One shots and such don't really apply. The second thing is that this reluctance only really applies to deadly situations that are the window dressing of scenarios, not major battles and situations that cap a campaign or arc of a campaign. The third thing is that this reluctance does not apply to situations where the PCs have ignored warnings and have bitten off more than they can safely chew. The fourth thing, and this is a big one, this reluctance completely burns off and is replaced by homicidal fury if players go against one of my named characters from fiction I've written about Hekinoe, but only if the players are the ones picking the fight.
Alright, so I don't like killing PCs. A lot of it has to do with knowing how much a character you created grows on you over sessions of play as you watch them evolve. I also don't like killing PCs partly because I consider my players friends. It also has a lot to do with DnD being cooperative, more or less heroic, fiction. Regardless of the nature of the PCs in terms of good and evil, the players are heroes and this is kind of their story. They are the protagonists. If we look at film and literature, most heroes don't die stupidly in random meaningless situations. There are caveats to this, and certain authors who seem to hate their characters and readers, but generally speaking, heroes don't die without meaning unless they act stupidly. Gandalf fell against a Balrog, allowing the ringbearer to escape. Boromir gave his life as penance so the halflings could escape because he felt the pull of the One Ring. Arthur, most commonly, fell to his son/nephew Mordred (sp?). Spock gave his life so his crew and friends could live.
So to me, the PCs are the stars of their movie/film and the story is about them, so to me they shouldn't die pointlessly in a random encounter or filler trap/fight/whatever. Unless they are stupid. If the guys are in a trap filled dungeon and someone pulls a lever without checking for traps and ends up in a vat of acid and can't make the Climb check to get out, he dies. If the PCs are clearly overmatched and still proceed to pick a fight, well, you asked for this.
I'm not one to fudge rolls excessively. I don't randomly convert a hit to a miss on my side or the PCs or a save into a fail, or anything like that. However, I do try to keep my players from biting it, because of all the reasons above. Sometimes I worry that this cheapens their victory, but I don't feel that's the case. The PCs are supposed to triumph over their faceless drone type foes. They're there to have their asses kicked. I design them so they can put up a fight and showcase how bad ass the PCs are, but I don't design them with the specific purpose of killing the PCs. Deliberately killing PCs is easy, I'm the GM, I have all of the things at my disposal. I literally have all of the power. I swear to Dog that it is harder to keep the dumb fucks alive than it is to kill them 90% of the time. Seriously? You pick a fight with an isolationist empire with a hard on for hunting and tracking and you just wander in and start killing them without concerning yourselves about things like tracking, magic, or Immortals? Right after hearing stories about how this one time some Giants picked a fight with these guys and the reprisals broke the empire of the Giants so much that it allowed their 4 foot tall slave race to stage their rebellion and win their freedom?
Alright, so I don't like killing the PCs and I do have a habit of helping the players without doing crazy things like completely ignoring the dice. However, I don't like doing this. My players know I GM this way, and while I don't think they count on it, they know I don't want to kill their characters. So it sits somewhere as background info or subconscious thought, so maybe they take chances they shouldn't. Maybe they're less attentive to detail than they should be. Maybe they're slightly more arrogant than their levels really entitle them to be. Maybe they do things like call their creators little bitches, not caring about the consequences to them, or the people around them.
I'm considering something like heroic protection. Something like players can't die in just run of the mill encounters or random encounters, unless it's something like falling into a pit of acid or a truly deadly fall or an unavoidable coup de grace. I'd have to come up with clearer cut definitions, obviously. Rules would operate as normal as far as unconsciousness and hit points, but instead of dying when you hit the appropriate negative number, you are mortally wounded.
If someone can get to you after the fight to restore hit points, you survive the encounter, if not, death. If you are restored or whatever, you gain a long lasting injury of some kind. Something that ignores hit point totals. Say you get arrowed nearly to death and become mortally wounded, but someone hits you with God Juice following the fight. You gain the mortal wound Arrow To The Knee or something and you halve your leg-based movement speeds, get a penalty to Acrobatics checks, can't run or hustle, and maybe a penalty to Climb checks as well. This is inspired by the injury system of FATE, just so you know.
This represents like an arrow splitting your kneecap and tearing out all the cartilage and whatnot. It is meant to cripple your character, because he got injured nearly to death. It is meant to be something that can be recovered from, but not simply by topping off your hit points. I'm thinking these sort of injuries would require something like the restoration spell to fix. It's a 4th level spell so it isn't just topping off their hit points by d6s, and it is geared towards restoring negative levels and ability drain/damage. It also has a 100 gp component cost, so it isn't something you can heal after you nap for a minute to talk to the Great Dog In the Sky.
I dunno. I'm not sure I like this system, and it would require a precise definition of when this mortal wound system would prevent death, but it does make it easier for a sometimes soft hearted GM to pull the kid gloves off and really truly hit the PCs with everything he has. But, it could kind of lead to players being a little more risky with their behavior against certain foes, relying on the fact that they have a buffer to keep them in the fight a little longer. I dunno, it's just something that occurred to me and I thought I'd type about it.