Jasper: Rule number one... never turn your back on your enemy.
The speeches given by Emmett, Jessica, Charlie and Renee at Edward & Bella's wedding reception.
Seth 90% of the time. Mixes this with being completely Adorkable.
At the wedding reception, Charlie is very subtly trying to hit on Sue Clearwater and offers to get her a glass of fancy champagne. Billy picks up on it anyway despite his discretion and cockblocks hilariously by turning his wheelchair around and nearly driving over Charlie's toes, forcing both Sue and Charlie to make some distance between themselves.
The scene where Bella drinks fresh human blood out of a plastic cup and remarks how good it is was either this or complete Squick for most of the audience.
The final battle turns out to be a vision Aro saw within Alice's mind. Tell me of a theater room which played this film and didn't get filled with laughter because of the massively trollish Mood Whiplash from this scene.
When this troper saw it, the elderly woman sitting in front of her at the theater stood up and did this:
So funny that the guys on the RiffTrax admit they couldn't possibly say anything to make it any better.
Also the follow-up scene when Aro is examining Renesmee and still giggling like a moron. Renesmee looks at Bella with a face that clearly says, "Is he always like this?" and Bella responds with a face that says, "I'm afraid so."
Maybe it's just me, but something about Jacob's fearful attempt to explain himself to Bella about imprinting on Renesmee was really hilarious.
And Bella sounding just as outraged about the Nessie nickname as the imprinting itself.
Really, everything about this scene is hilarious - Rosalie and Emmett are both gleefully anticipating Bella's reaction to Jacob's imprinting. Then Jacob gets dragged outside by Bella and Bella kicks Jacob's ass. Jacob rationalizes that imprinting is something he can't help, and that Edward hasn't killed him for it so Bella shouldn't either - only for Edward to not that he's still debating it. All the Cullens become mildly amused at Bella's new strength as she continues to wail on Jacob. Then Esme advises Edward to stop Bella, to which he casually responds, "[Jacob] said he can handle it." THEN Jacob mentions the nickname...
When Bella and Edward present Charlie with a fishing trip for Christmas as an excuse to keep him away from the upcoming showdown with the Volturi, he jokingly asks "trying to get rid of me, eh?" The two of them fumble around for a bit, attempting to think up a lie, then he responds "because it worked!"
A couple involving Wolf-Sam in Alice's vision battle. First, after the fissure gets opened in the middle of the battlefield, there's a shot of Sam leaping across the fissure and tackling a Volturi Mook hard enough to literally knock the guy's shoes off. Secondly, when Alice tosses Jane down in front of Sam, he's casually carrying the severed hand of another Volturi Mook in his mouth.
It should be noted that the reason he's so aggressive in the first place is because some Volturi just killed his ex-girlfriend and her brother.