After spending a lot of the movie subtley putting Jane down and undermining her, Jane and Ricky's verbal bitch-slap to Angela is pretty satisfying:
Angela: Jane, he's a freak!
Jane: Well SO AM I! And we'll always be freaks and you never will because you're just\\ \\too...perfect.
Angela: Yeah, well, at least I'm not ugly.
Ricky: Yes you are. And you're boring. And totally ordinary. And you know it.
Lester blackmailing his boss on his way out the door, including threatening to lie that the guy came on to him, knowing people will want to believe it.
Lester quitting his job, and pretty much everything he does after.
Lester catches Carolyn red-handed when she shows up along with her lover, Buddy, at the burger joint where Lester works. Rather than losing his temper, Lester gives her polite responses that are positively dripping with sarcasm. When Carolyn tells him to stop, Lester flatly tells her "No, you don't get to tell me what to do. Ever. Again."
Ricky has two in swift sucession: Telling his father that he's a gay prostitute, just to mess with his head, and then telling Angela that she's 'ugly, boring and totally ordinary' to get back at her for being a bitch to Jane.