A lot of NPCs have no part in the main quest line yet being flagged as essential. I would really love to have the option to do things such as finish the war by assassinate the important figures. I understand it svcks when you accidentally breaks an epic quest chain, but how about when your target is unconscious, one more blow can send him/her to the oblivion? This way you know the target is important but still get to choose to kill him/her if you wish so.