Melia: He's (Riki) so cuddly I could almost cuddle him to death.
Dunban: Riki may be the softest of all Nopon.
Riki: Riki suddenly feel afraid.
Reyn: Just goes to show, brawn is better than brains.
Sharla: Oh, I can't let him stand for that.
Melia: The head, shoot him in the head!
Reyn: What, what did I say?
While it isn't all three character interacting this is a pretty funny one:
Reyn: Sharla, did you see me?! Did you see what I did?
Sharla: Oh, I wasn't really looking.
Reyn: Oh come on! That ain't fair!
In fact each of the 37 potential combinations(35 threes and two early-game duos) of characters has an amusing post-battle quote. Most of them are pretty good and they don't repeat often enough to become grating.
Some of the item descriptions are also pretty funny, for example
Rotten Meat: Best avoided. Sold with a certificate guaranteeing gastroenteritis.
For added Genius Bonus, watch carefully how Melia, Shulk, then Reyn punt Riki around in the air: it's a legitimate volleyball play.
The end cutscene has a few good scenes, from the fishing antics between Reyn and Riki, to Shulk awkwardly pretending not to notice that Fiora got her old body back, changing the subject to her hairstyle of all things.