It would be extremely awesome to be able to do this in the next ES game.

Also head shots with the bow would be good.

what kind of headshots exactly? the ones with blowing heads?

And by the way, this belongs to the ideas and suggestions thread.

Critical damage is what simulates stealth kills, like throat-slitting.

A throat-slitting animation might be cool. But a button to just slit the victims throat would be kind of lame, IMO. Too action gamey.

As for localized damage, I like that idea a little more.

I was thinking there should be an option to 'grab' the opponent... grabbing would be next to impossible in open combat, so it would require a stealthy character to sneak up behind and grab them. Once grabbed then there could be the option to cut their throat and kill them, although for tougher enemies may fight you off before you get the chance.

Play the mod "Deadly Reflexes," makes combat a LOT more interesting, and has throat slitting (but you need a good sneak skill for it to work).

The Mark of Kri game has some creative stealth kills.

twisting necks
impaling with spear
decapitation with axe
headshot/neckshot/heartshot with bow
suffocation/strangulation
hiding behind a corner, then reaching out and pulling the enemy back around and then repeatedly bashing his brains out against the wall (with one hand covered over the enemy's mouth so he can't scream)

Don't let it's cartoonish style fool you, that game is quite visceral.