The conversation between Ike, Soren and Aimee in Radiant Dawn. The whole thing: Aimee's plan to seduce Ike by forcing him to confess and then spreading rumors of it, Soren's dramatic rescue and "What I do now, I do for the company," Aimee's horror at being left alone with Soren, and then Soren's lady-killing speech... Priceless.
"You're a diamond, and other beorc only glass beads, Miss Aimee. ... ... Stay beautiful."
Soren's advice on how to keep Volke in check:
Soren: I believe this will be a good opportunity. We will almost certainly have need of this man's talents. He is a dubious character at best, but at least we know his motives: everything begins and ends with gold. He'll be easy to control.
Oscar: Hi, Kieran. How are you? Kieran: What the... Oscar! How I loathe that name! Don't give me such pleasant greetings! I care not for them! Oscar: What did I do now? Kieran: Oh ho! Don't tell me you've forgotten our second year of enlistment! The year we completed horsemanship? There was a final race to end the year... My beloved horse and I were flawless, but you beat us by the smallest of margins! Oscar: Huh? Oh, are you talking about that race you challenged me to? Yeah, that was fun... But I thought the distance between us was at least three lengths— Kieran: Ha! LIAR! Deceitful, lying, squinty coward! That was the very moment I marked you as my archrival! Don't pretend not to care! Oscar: Uh...wow. I had no idea— Kieran: But why!? I must know why you left the Crimean knighthood without a word of explanation! I devoted myself to training with my horse! I worked day and night so I could best my archrival... And thanks to my extreme devotion... I didn't realize you were gone until six months later! Delinquent! Reneger! Oscar: Wait a sec... Kieran. How is that my fault?
Kieran is in Large Ham mode even long before that: when you first meet him in Path of Radiance. Open his jail cell and use Oscar to talk to him. You won't regret it.
Oscar: You're from Crimea, right? Come on—we're here to rescue you. We've opened your cell. Now's the time to escape. Kieran: Ah! It's you! I could never forget that squint! Knights of Crimea, twelfth regiment...your name is Oscar! Oscar: And you're... Wait a moment...You're Kieran, right? Kieran: That is correct! I am Kieran...The same Kieran who has sworn himself to be your eternal rival! Oscar: Uh...Right...Kieran...So...how've you been? You look good. Kieran: As always, your manner is listless and inappropriate. It befits one who would call me foe! You were discharged three years ago...What are you doing here now? Aha! Could it be...You dastard! You've turned your coat and gone over to Daein, haven't you? Rarrrrr! What despicable, contemptible behavior! Unforgivable! Have you no shame? You were my one true rival! Where has your pride gone? Oscar: The mercenary company I'm attached to serves under the command of the princess of Crimea! We came here to free any Crimean prisoners. Kieran: The princess of Crimea?!? You're not part of the royal guard! How do you know about the princess? Oscar: Well, like I said, the princess is our employer and— Kieran: Aha! So that's your scheme, is it? You hope to distinguish yourself by meritorious service and gain the glory that is rightfully mine! Admit it! Oscar: Look, my duty is... Kieran: Blast you! Curse your name! Curse the name of Oscar and all who call him kin! I will never let you surpass me! Princess! I'm coming! Kieran will be forever at your side! Oscar: Whoa...He's even more excitable than I remember. Hard to believe he's actually a decent knight...
Pretty much anything involving Oliver. He acts about as obsessively bishonen as Yumichika...never mind the fact that he's a delusional gonk.
It gets even better when he joins your party in Radiant Dawn. Especially if you have Ike talk to him immediately afterward. The last line of their conversation is just priceless.
Ike: Listen...Would you mind rejoining the enemy?
This one's pretty good as well.
Sephiran: Duke of Tanas, imagine seeing you here!
Oliver: Lord Sephiran, as lovely as always. But has it come to this? Must we fight to the death, and deprive the world of one of our beautiful countenances? Can other lovers of beauty endure such a loss?
Sephiran: I confess that your presence has me bewildered. Could this be part of Yune's plan? I simply never would have imagined you here. Your presence proves that Tellius is unraveling at the seams. Judgment cannot come soon enough.
The entire recruitment conversation for Largo in Path of Radiance is one long CMOF. It starts with Largo bragging about how he's a "world-class berserker" and asking to see the general (not expecting it to be someone as puny as Ike). After lampshading how familiar this sounds (re: Calill's recruitment), Ike tries to hire him, and Largo initially laughs it off until Calill interjects and asks General Ike if he's going to hire Largo.
Sanaki: Still no word from the battle. What's going on out there? I should go to my people. They may need me.
Naesala Hey, just where do you think you're going? Do you think the high-and-mighty apostle should be traipsing around a battlefield, hmm?
Sanaki: Wha— Oh, it's just you. Hmph. How dare you sneak up on me that way!
Naesala: That beauty from the Holy Guards told me to keep an eye on you. So, do me a favor and sit still, will you?
Sanaki: But I can't see anything from here! I have to know how my people are faring down there! I...I can't bear doing nothing! Hmm... I have an idea. You! Carry me to a place where I can observe the battle! Don't give me that look! You're the one who agreed to guard me, so do your duty and obey your orders! Come on, let's get moving!
Naesala: Wait a minute... Is that what passes for beorc logic these days? No wonder you've lost your throne. OW! Stop that!
Sanaki: Are you going to obey me, or shall I have you chased back home in a cloud of feathers?
Naesala: By the goddess, what have I gotten myself into? As you wish, Empress. My back is yours.
What makes this even funnier is that Naesala is off-screen and credited as "???" up until his last line—we don't even get the slightest clue as to whom Sanaki is talking to until he mentions "beorc" logic.
Sanaki: You finally made it, Sephiran. Sephiran: Sanaki, I... Sanaki: I was starting to wonder how I would punish you. Sephiran: I'm sorry? Sanaki: You are my subordinate, after all. I have decided that leaving one's empress to die is punishable by drowning in a pool of rancid butter. Sephiran: Of course it is, my empress. Sanaki: I hope you're a strong swimmer.
She's also responsible for one more, though not directly involved in it.
Lekain: Tah ha ha... So nice to see you, King Naesala. When you can't oppose me, that is. Your blood pact means that you'll have to betray your companions...yet again.
Naesala: Not today, actually.
Lekain: What did you say?
Naesala: Sorry to break it to you, Lekain, but I have recently...been promoted, shall we say. I now take orders from over your head, Vice-Minister. From Empress Sanaki, to be exact.
Naesala: The curse of the blood pact applies if the master's orders aren't obeyed, but by the law of Begnion, you're overruled. So, Lekain, right here, right now... I'm going to tear you apart, as I've been wanting to do for years.
When Ike's team gets on a ship to set sail for Begnion, Ike seeks out Volke to ask why he never shows up for any company meals after his sister expresses worry that Volke must be starving to death, since she never sees him eat. When Volke says that he doesn't like crowds and points out that Ike never had a problem with it when they were on land, Ike replies:
Ike: Okay, listen: Land? Big. Ship? Small. It's not the same!
The last part of Pelleas's conversation with Sephiran is both hilarious and gross. At the same time!
Pelleas: I think I'm going to be ill...
Sephiran: Be assured that you were essential to Daeinís reconstruction, which was a vital step toward waking the goddess. Fortunately, Izuka was able to use you to execute my plan.
Pelleas: You are going to pay! You are going toÖBLAAARRRGH!
A weird example that involves gameplay rather than dialogue. Chapter 3-11 of Radiant Dawn is littered with pitfall traps, which the enemy always avoids stepping on as well. However, an enemy bishop in that level has a Rescue staff and can warp another unit onto that spot. This can allow a unit with Pass to pass through a trap without incident, but the truly funny part is when a ground-based unit with Canto attacks the enemy, destroys it, continues movement into the space that was just occupied by an enemy... and promptly falls into a pit.
Volke has exactly one support partner in FE9: Bastian. From the first line of their C support, you know this is going to be good.
Volke: You there, in the bushes. You have until the count of five to show yourself before I start throwing sharp objects. One...two...four...
Black Comedy at its finest, from the boss of chapter 22 of Path of Radiance.
Schaeffer: "...Gwaar... Haaaarr... Haaaaaa... Shoulda brought... more priests... Or some... babies... Dang..."