Every single one of Sephiran's pre-battle convos, especially Sanaki, Ike, and Sothe's.
Sanaki: ...Sephiran... Everything you ever told me, every time you gave your hand to me, every time you smiled... They were all lies? ...You're the most appalling fraud I've ever known! Sephiran: No, Lady Sanaki... I've actually lied to you very little. What I have done is hold things back. I've also twisted the truth from time to time... But I have only told one blatant falsehood. That one lie has weighed heavily on me. It makes me hate myself sometimes. Sanaki: Sephiran... Sephiran: I always care deeply for you, my little Lady Sanaki... You are my sun and moon. I never wished to harm you. Please... You must understand... Sanaki: ...No! Sephiran, no!
Ike: I have to ask, Sephiran. What are you after? What's this all about? Sephiran: Why do you wish to know? You would achieve nothing by learning my reasons. You would help no one. I lost faith in lesser beings, and desire an end to them. That's all. Ike: So why did you save me on that day? Sephiran: May I ask you a favor, Ike? Tell me how you feel about it now. Can you bear recalling those horrific memories? Ike: Yes... I'm fine, now. But I suppose at the time I wouldn't have been able to take it. Sephiran: All beings endure tragedies for as long as they continue to live. It has always been the case that suffering is unavoidable. And this grim reality plays out over and over, in every country, under every ruler... As long as there are beings who feel, they will feel pain. Ike: So what? We should all just give in and die? Put it behind you. Deal with it. Sephiran: Do not make light of this... Ike: I'm not, Sephiran, I'm extremely grateful that you once helped me through a terrible time. But I have accepted that occasionally we all have to deal with hard times. I've had pain, I've had suffering, and I have gotten up and moved on. I don't try to forget what happened that day. I just accept it... And neither that or anything else will ever stop me. Sephiran: You are a strong man, Ike, son of Gawain. But not everyone is as strong as you...
Sothe: Here goes... Sephiran: Hello, child... I'm a little surprised to see an ordinary boy like you, fighting for the world. This day is full of surprises! Sothe: No one's more surprised than me. I can't read people's feelings like Micaiah... I'm not invincible in battle like Ike... Between all these laguz kings and great beorc heroes, I don't really belong here. Sephiran: Then why are you here? Sothe: Because there's one thing that I can't afford to lose. Micaiah. I've come all this way just to protect her... I won't lose her now. Sephiran: The depth of your feelings... Might I ask your name? Sothe: Sothe. Now if you want to stand in our way, I'm prepared to cut you down.
Sephiran/Oliver is another personal favorite, but that's probably because I think Sephiran makes a hilariously good point in it. That chapter in general just has fantastic dialogue.
Also, there's this gem of a moment in Awakening.
Sumia: Snap out of it, Captain! slugs Chrom in the face Chrom: Ouch! ...What the hell was that for?!
In my eyes, that will forever be known as the single funniest moment in Fire Emblem history. Love hurts, indeed, Flavia, love hurts indeed!