It'd be incredibly useful for us thieves. That way we don't have that deer in the headlights look when someone wakes up and catches us rummaging through their house, we can just blast them up against the side of their head before slipping out.
It would also be useful for thieves and assassins when engaging a mob of enemies. Sneak up, knock one of them unconscious, do some knife work on the other guy and finish him off just as the other one is coming back to his senses before you slice his throat.