Emily Don't Burn :(
You want to know what really ticks me off about this otherwise excellant game? You can kill most of your allies in the framing levels at the pub in the early stages of the game, and yeah, it prompts a "game over" screen just a couple seconds later. I admit, it doesn't really serve any purpose unless you just feel like going postal on your bossy bosses ;) and sometimes it's just fun to watch stuck-up pendleton running around on fire.
But the annoying part is that you can kill everyone but Emily! Trying to kill her doesn't even prompt a "game over"! What's up with that? The worst part is how extra annoying she becomes when you try to kill her. You can stand right in front of her and shoot her in the face, and not only does she survive without flinching, but then she says something annoying like "Was that you, Corvo?" What is she? Crown princess of the friggin obvious? :p
"Feeling Stupid? I know I am!" - Homer J. Simpson