OT: What is your name again? Barbaro?
SS1: Obara.
OT: Obara. You look like an angry little boy. Don't presume to tell me what I need.
SS2: Forgive my sister, what she lacks in...
OT: Do shut up, dear. Anything from you?
SS3: I...
OT: No? Good.
Seriously, I just fucking love Olenna Tyrell and the way she delivers every single one of her lines. Besides, to have her destroying no one else than the Sand Snakes... That was glorious.
Others:
Cersei's confession to Unella, and:
U: I'm ready to meet the gods.
C:
What? Now? Today? You're not going to die for a long time. This is Sor Gregor Clegane. Your gods have betrayed you. This is your god now.
(Damn, that was creeeeeeepy!!!)
Walder Frey: What is it that you fight for? Beating your enemies? Well, I've beaten mine.
(Say what you will, the man did piss on everyone he wanted to, in the end. He was a coward but played the Game fairly well, unfortunately).
Lyanna Mormont's speech was also epic.