10. Kiss Kiss Bang Bang
Perry: Look up "idiot" in the dictionary. You know what you'll find? Harry: A picture of me? Perry: No! The definition of the word idiot, which you f**king are!
This insult is genius because it wrong-foots both Harry and the audience. Everyone's expecting him to do the same tired old joke about seeing a picture of yourself in the dictionary under some generic insulting word, but he completely turns it on its head. Not only does he call Harry an idiot, he makes him feel foolish for falling into the trap Perry laid for him. So basically, he's calling him stupid, and then providing evidence to the fact. A double burn.