Pretty much any scene in which both Syrenne and Lowell are involved.
Syrenne's description of the Arena.
Both of the bath scenes.
Any scene Syrenne is in, honestly.
The entirety of the Haunted Mansion chapter, particularly for normally calm and collected Yurick's hilarious reactions to it.
For being purely a sight gag with no dialogue, Zael's reaction to the Fortune Teller is priceless. She spouts her usual generic info about frogs or cats, and he throws up his arms in glee, shakes her hand excitedly, and then jumps up and performs a little cheer like he's won the frickin' lottery.
This exchange between Asthar and Therius, where the former explains to the latter that he doesn't need to be so uptight all the time. Needless to say, Therius doesn't quite get it...
Asthar: Indeed! Sir Therius, when the time comes, you must work together with that person.
Therius: Yes, General! It will be as you wish!
Asthar: ...Therius, it's just you and me. No need to be so formal.
Therius: As you command!
Asthar: Therius, I just said not to...Oh. No wonder you're not a hit with the ladies.
During one of the first boss battles you're facing off against a gigantic armored monster. What does our resident Mage Mirania think it looks like? A giant muffin.
After Zael refuses his Knighthood he's stopped by Dagran on the way to Calista's room, who begins to complain about all he's done to get Zael to become a knight, but even after Zael acknowledges and apologizes, Dagran draws his sword dramatically and exclaims "looks like I'll have to stop you by force!" Zael looks at him for a second, apologizes again and then walks past the sword.
When the knight captain Baron Huge (yes that is his name) and his goons are getting their asses kicked by a giant ogre, he starts shrieking for help from the party. Syrenne just looks at him funny and ignores him, until he (while in the middle of a fight no less) prostrates himself and starts BEGGING for her to help him. After you kill the ogre, it then falls on him, pinning him to the ground. Syrenne takes advantage of this and lectures the guy before leaving him there under the big stinky ogre.
During the Epilogue in the final Arena Season, the 3rd round reunites Zael with the Gurak Captain. Both Syrenne and Lowell weren't present during this chapter so they ask Zael who the hell is this guy, and Zael kind of stares blankly and says that he has no idea. The Captain is a million kinds of pissed as he calls out his new pet, Ghoul to take out the party. Ghoul instead squashes the Captain flat, which makes Zael recall him. Vaguely.
Gurak Captain: Now then, let me introduce you to my new pet! (He then gets flattened)