Quite possibly everything said by Fat Amy and Lilly.
To put it into perspective, while driving to finals Lily sits behind the driver, Donald, who is beatboxing. Afterwards, she quietly joins in, to which he comments that she's pretty good. And then she goes out and says "I set fires to feel joy." In the sweetest, quietest voice possible.
And Donald's response:
"That's adorable."
And yet another Lilly moment, while the Bellas are confessing their issues and problems to each other, her chosen fun fact was that she'd eaten her twin in the womb.
Lilly's introduction at the audition. If you can read lips, or turn the volume up she says she has gills like a fish. Not only does she repeat that fact when they ask her to speak up, but she actually does a fish like twitch with her mouth.
Her disturbing non sequiturs make her firing an imaginary shotgun at the Treble Makers even more funny, because she could actually be serious.
The moment when Lilly finally speaks above a whisper.
Fat Amy: Excuse me, bitch, you don't need to shout.
A lot of the banter between John and Gail.
Fat Amy's horrified screaming when Aubrey finally loses it and vomits all over the place.
"ENOUGH! ENOOOUGH!"
The Bellas practicing their choreography, with some hilarious vocal exercises and dance moves.
Amy: I sometimes have this feeling that I can do crystal meth, but then I think, hmm...better not.
Twice as hilarious when you find out that their subplot was improvised by the actors throughout the entire film, and Bumper trying to kiss Amy was something the two actors experienced backstage.
Jesse's random call-outs/commentary right in the middle of his audition. Also kind of awesome, because he threw them in his breath breaks and didn't miss a beat of the song.
Aubrey: We shall begin by drinking the blood of the sisters that came before you. Beca: Dude, no.
When Aubrey is criticizing the members and gets to Jessica and Ashley, who have barely been shown on-screen since their induction.
Aubrey: And Jessica and Ashley, it is like you haven't been here all year long. Jessica: Aubrey, really? Ashley: We've literally been here the whole time.
Pitch Perfect 2
After Beca and Chloe have an argument:
Fat Amy: You're Beca and Chloe! Together, you're "Bloe", and everybody loves a good blowy.
Beca inability to hide her attraction to Kommissar, the female leader of Das Sound Machine, and Kommissar's nonchalance about it
Beca: You are physically flawless.
Kommissar: Thank you.
Beca: But it doesn't mean I like you.
Lilly cutting Beca down from the net trap and then saying it's because she sleeps upside down like a bat.
When asked what she's going to do after she graduates, Lily says travel through time
The Green Bay Packers, of all people, are one of the groups that got invited to compete in the riff-off at the home of the eccentric rich guy. Surprisingly, they're not that bad.
Everything about the Green Bay Packers' appearance, but especially their straight-faced performance of Bootylicious.
Beca's boss (played by Keegan-Michael Key) being constantly frustrated with the intern Dax:
Beca's Boss: Dax, go and eat your lunch in the corner... GO, DAX!
Dax: But what will I do with my Sriracha?
Beca's Boss: Say one more hipster thing and I swear to god... [kicks Dax's chair away]
Also, the fact that he can't be bothered to remember any new people's names.
Beca's Boss: Good job, Reggie!
Beca: [to Emily] ...I'm Reggie.
The continuation of Fat Amy and Bumper's subplot from the first movie.
Pieter refers to Fat Amy as 'Flabby Abby':
Fat Amy: That's not my name.
Pieter: I don't know your name. Could be anything. Obese Denise, Inflexible Tina, Lazy Susan...
Fat Amy: Mein name, ist Fat Amy. Und I eat krauts like you for lunch!
This:
Kommmissar: I'm sorry, I don't speak Loser - what did you say?
Pieter: She actually speaks eight languages, but Loser is not one of them.
Also in the riff-off, when the category "I Dated John Mayer" comes up and Bumper breaks in with What's Love Got To Do With It:
Sir Willups Brightlymoore: It's funny... for everyone, because it sounds like you're implying that John Mayer and Tina Turner are having...
Bumper: Oh yeah!
[crowd boos]
Pieter: Get him out, get him out!
After Cynthia Rose is accused of blaming the minority (Flo) in the group:
Fat Amy: I'm not pointing the finger at anybody. (Beat) It was Legacy's fault.
(cut to Emily bewildered by this)
Beca gets caught in a booby trap at the retreat and thinking she’s about to fall to her death begins confessing her other secrets to the other Bellas, resulting in this exchange:
Beca: Jessica and Ashley, I don’t actually know which one of you is which!
Jessica and Ashley: I’M JESSICA— (they stare at each other, confused)
Pitch Perfect 3
When Aubrey tells the Bellas that her dad has got them a spot for the USO tour:
Chloe: To sing?
Aubrey: No, to do military black ops.
(Lilly looks excited)
Aubrey: Yes, to sing!
(Lilly looks disappointed)
Stacie gets around so much she doesn't know for sure who the father of her baby is.
Fat Amy commenting on the band name of one of their rivals (Evermoist):
Fat Amy: My grandma is in a band. Nevermoist.
Jessica and Ashley remain background Bellas, but at least they are each given separate lines this time.
Jessica: Did she just say our names?
Ashley: Don't be stupid.
When Fat Amy is threatening her father over the phone, after he kidnapped the Bellas:
Fat Amy: I swear to god, if you hurt any of them! (Beat) Except for Jessica and Ashley...
And immediately after:
Fergus: So... which two of you are Ashley and Jessica?
[Everyone, including Jessica, points to Ashley]
Ashley: Ah, shit.
Lilly finally talking at normal volume:
Lilly: Cool beans.
(all the Bellas are completely speechless)
Beca: You talk?!
Lilly: Satan has finally left my body! Hi, I'm Esther.
(cut to Flo making a praying signal as the others laugh with confusion)
Beca: Okay, I have so many questions.
The last scene has John giving Gail an Anguished Declaration of Love, then both of them break down laughing, knowing he's faking it.
As part of a plan to rescue the kidnapped Bellas, Beca has to slip in with the rest of the group and initiate a distraction. When she starts speaking, Fergus immediately notices that she wasn't there before - her cover story is "I was here this whole time; I'm just very small".
After Emily suggests that the Bellas go to DJ Khaled's hotel to see if he'll give them a better shot, Fat Amy has this lovely insult:
Fat Amy: Emily, I can't believe that a half-decent idea came out of your dumb mouth.
(Fat) Amy, and her response:Amy: (walks up to Bumper and Donald) Oh hey, what are you turd burgers talking about? Dressing for comfort?Bumper: You...are probably the grossest human being I've ever met.Amy: Well, you're no panty dropper yourself.Bumper: So, I have this feeling that we should kiss. Is that, like- like a good feeling, or...Amy: I sometimes have this feeling that I can do crystal meth, but then I think, hmm...better not.