Perhaps the most famous moment in the entire book: It's the midpoint, and after a particularly nasty court case (orchestrated by Toohey), Roark's career has been tarnished for what looks to be a really long time. Roark shows up one night at what was this close to being his architectural masterpiece, to look at what it's become. Toohey shows up, and tries his best to get some kind of reaction. Roark just makes like The Stoic. Finally, it's Toohey that loses his cool, and:
Toohey: Mr. Roark, we're alone, here. Why don't you tell me what you think of me? In any words you wish. No one will here us.
Roark: But I don't think of you.
Roark's Badass Boast early on: when someone asks him who's going to let him see his designs through, he says, "That's not the question. The question is: Who's going to stop me?"