This one might be a little goofy, but here goes:
I love the nonlethal approach.
I explicitly try to kill as few things as I possibly can whenever I have a realistic nonlethal option for dispatching enemies in games, and I feel the highest vindication whenever the game, world or characters reacts to those actions.
These options are common across many shooter/FPS hybrids--Deus Ex, Dishonored, Alpha Protocol, etc. But after recently finishing Dishonored it occurred to me that I'd never seen this option in any Infinity Engine RPGs or really any pure Western RPGs that I could think of at the time, and I began to wonder why not?
Most tabletop RPGs, D&D included, have at least a short barely-referenced sidebar on how to deal nonlethal damage and knock somebody out in a fight, why has this never been an option in the classic or modern pure western RPG? Sure it's a bit silly, since most of what you're cutting down are nameless orcs, thugs, kobolds, and other miscreant cannon fodder, but I've always believed the mark of a true hero is restraint: Just look at Batman.
It would be nice to have a game where my diplomat knows some martial arts focused strictly on rendering opponents unconscious when things get hairy, I would prefer to walk away like a smug badass saying "I warned them" when negotiations fail. Usually, instead I just shake my head and sigh mournfully at the lives wasted this day, because the option to do anything but set them on fire isn't ever present.
Granted, I eventually become desensitized and then when negotiations fail I just cackle like a maniac as I introduce them to a colleague of mine: Doctor Force Lightning, Ph.D. in Murder
From a development standpoint, adding in options like these seem pretty trivial, depending on how deep you wanted the system to be. A good 90% of it would be minor subsystems in the game logic--a bool or two here, a different value there--I'm not asking for much, just a little confirmation that I left those dumb thugs on the street battered, bloody, but still breathing. It's not like anyone's going to carefully examine the character model and check to make sure they're using the flat-edge of the blade, so unique animations aren't really necessary I'd say.
Don't suppose there's anyone out there who shares my sentiment?