I've been running Age of Worms, and all the pc's have an armband that they can use to send the whole group to a tavern, where they have to go into a random dungeon and retrieve an item, then they can go back to where they were or to a friendly town that they know of. They haven't used it yet, but they have had a few almost TPK's, but have stuck it out and won. The armband also lets them be raised once, but the 2 that have died have decided not to be raised, and brought in new characters. I don't try to kill pc's, but i don't work too hard to prevent it, unless it looks like a TPK, when i will let the monsters make decisions that may not be the smartest, but the dice still get to decide the fate of the pc's.