Having just finished dishonered I think it would be awesome if a non-lethal playthrough style could be implemented in this game. There could be tazers, phasers, sleep darts, electric boxing gloves or craftable electric baseball bat as well as good old fashioned fists or the trusty blackjack for stealth type characters. Anesthetic "poisons" could be applied to weapons or maybe even to some ammo types to create more versatility and more options for not having to kill everything in sight.
All weapons should do a comparable amount of damage to regular weapons except instead of death when HPs run out, characters and creatures are rendered unconscious instead (and just as lootable except for maybe creature body parts). Knockout time should probably be in the vicinity of a day or so of game time. Once you're knocked out with tranquilizers it's not likely you'll get up again just because a friend shakes you, much less aim weapons.
It would really be fantastic to see this kind of gameplay possible in Fallout 4, I hope it's not too difficult to implement as a Mod!