If there is but one moment to choose, then let it be Angus' fantastic "The Reason You Suck" Speech to Rick at the dance, shown here in its entirety:
Angus: I'm still here, asshole! I'll always be here! You push me down and I'll get back up again, and again, and again!! I can beat you right now, but I don't wanna be better than you, Rick! I don't wanna be better than anybody! I wanna be who I am: a fat kid who's good at science, and fair at football; that's who I am! I can live with it, why can't you?
Rick: Because it's not normal! You're not normal!
Angus: And who is normal? You?!
Rick: You bet your ass!
So what, to be normal we all have to be like you? There are 400 people in this building that are nothing
like you! Some of them are fat, some of them are skinny, some are tall, some are short. Some of them have braces or birthmarks, or scars or frizzy hair, or ears that stick out! (Angus' big-eared friend Troy stands up)
and most of them walk through those halls every day, never telling anyone the truth about what they really want, or need, or believe, because people like you, "normal" people like you, have them terrified of being who they are. I mean, if you're normal, what does that make them? ...So which is it, Rick? Are you "normal," or are you just one of us?
Rick: Whatever I am, it's something you're never gonna be.
Angus: ...Thank God.
(The auditorium erupts into applause, as does the audience)