It is quite difficult to find these in this book, but...
The early scene where several characters are Polyjuiced into Harry Potter decoys, including twins Fred and George. Their reaction? "Wow, we're identical!"
From the same scene, Harry's reaction to seeing all his doubles changing their clothes: 'He felt like asking them to show a little more respect for his privacy as they all began stripping off with impunity, clearly much more at ease with displaying his body than they would have been with their own.' Ron exclaiming (in a Shout-Out to a joke made in Half-Blood Prince about Harry's chest), "I knew Ginny was lying about that tattoo," can only be topped by this moment after Bill offers to take Fleur on a thestral: 'Fleur walked over to stand beside him, giving him a sappy, slavish look Harry hoped with all his heart would never appear on his face again.'
Fleur, upon turning into Harry (with the real Harry standing right there): "Bill, don't look at me; I'm 'ideous!"
Hermione's innocent innuendo: "Oh, you look much tastier than Crabbe and Goyle!" and Ron's reaction.
And later still, after George has lost his ear and makes his horrible pun 'I feel saintlike... holey', Fred's reaction: "Pathetic! With the whole wide world of ear-related humor before you, you go for holey?"
During the preparation, when Molly orders Ron to clean his room and he refuses.
Molly: Your brother is getting married in a few days! Ron: And is he getting married in my room? No! So why in the name of Merlin's saggy left— Arthur: Don't argue with your mother.
The drunk relative trying to figure out if Polyjuiced Harry was his son.
Charlie, Hagrid, and another wizard getting drunk and singing about Odo the Wizard.
Aunt Muriel (and how she looks like a "badly-tempered flamingo") and Ron's response to her.
Ron: Nightmare, Muriel is. She used to come 'round every Christmas until, thank God, Fred and George put a Dungbomb under her chair and she took offense. Dad always said she'd write them out of her will.
Hermione trying to kick Ron under the table and hitting Harry instead.
Ron saying about Muriel, "She's rude to everyone" and George comes up saying "Talking about Muriel?" He follows this up with, "She just finished telling me my ears are lopsided."
The descriptions of Ron's uncle and how he celebrated at parties.
Fred: He used to down an entire bottle of firewhisky, then run on to the dance floor, hoist up his robes, and start pulling bunches of flowers out of his—
Ron to his daughter, Rose: Thank God you've inherited your mother's brains.
Fleur's transparent attempt to break the tension between the newly-arrived Percy and the rest of the Weasleys by asking Lupin about how Teddy is doing. Lupin catches on and loudly announces that he's got pictures, desperately trying to shove them in everyone's faces.
Kreacher: *after Harry stops him from knocking out Mundungus* One more for luck, Master Harry?
Peeves calling Voldemort 'Voldy'.
We did, we bashed em!
Wee Potty's the one!
Now Voldy's gone mouldy, so now let's have fun!
Ron: "Really gives a feel for the scope and tragedy of the whole thing."
The scene when they're about to leave the Dursleys' has some good ones.
Harry: If you think I'm going to let you risk your necks for me—
Ron: "I don't know how to break this to you, Hermione; but I think they might have noticed that we broke into Gringotts."
When the group gets attacked while sitting at a pub, during the fight we look into the kitchen and see the attendent just standing there obliviously enjoying earpiece music while the whole area outside gets trashed.
Harry is searching Umbridge's office and finds a book titled "When Muggles Attack".
Just before going in the elevator, Ron, in disguise recieves some disturbing news. Apparently his wife is in court. He's actually quite worried about it. Until he's reminded...
Harry: Ron, you don't have a wife.
Shortly afterwards, they discuss what happens if they can't find Umbridge, only for the elevator to open with her standing right there.
Any of the Polyjuice Potion sequences—Harry, Ron, and Hermione looking freaked out in the guise of Ministry employees (one of whom is the normally badass Runcorn) and then Hermione-as-Bellatrix, trying so hard to look dangerous.
Hermione!Bellatrix: [awkwardly] Good morning.
Harry: [under the Invisibility Cloak] "Good morning? Good morning??" You're supposed to be Bellatrix Lestrange!
"Just keep telling her about that ball of light going into your chest."
"Hermione, when have any of our plans actually worked? We plan, we get there, all hell breaks loose!"
Neville's reaction during the final battle when Scabior takes that first step across the barrier.
The kiss between Harry and Ginny in Part 1, which was observed by George as he dances into the room with a toothbrush in the hole where his ear used to be. When the two break the kiss and look at him, he gives a sly grin and says "Mornin'."
After getting blasted by Voldemort from the courtyard all the way back into the Great Hall, Neville comes to in the most serene and blissfully unaware way possible, while all hell's breaking loose around him.
When the trio returns to Hogwarts, Harry and Ginny have a Held Gaze moment. While Ron grins and waves in the background, then complains to Hermione about being ignored.
Ron running after Goyle after he tried to AK Hermione, yelling "THAT'S MY GIRLFRIEND YOU NUMPTY!" then a minute later he comes running back screaming "GOYLE SET THE BLOODY PLACE ON FIRE!!" grabbing Hermione and leaving Harry!
Not to mention Hermione's expression during this. She has a moment of 'Hehe, I'm his girlfriend!' before shooting a 'Don't. Say. A. Word' look at Harry.