Just thought of a few more...

Celes: Aren't you a little short for an imperial trooper? (this line was used again in FFVIII, if I'm not mistakin)

Aerith: This guy are sick.

Squall: I dreamt I was a moron.

Squall: I'm not your mom.

Eiko: What a bimbo!

Eiko: Garland? Now that's a sinister name!

Quina: I... so happy. (when Quina and Vivi get married)

That one moogle whose name escapes me: I'm kupo for kupo nuts!

Rikku: Memories are nice, but that's all they are.

Ashe: You're sky pirates aren't you? Then steal me.

Ashe: Don't interrupt me!

Vaan: How old are you again?
^ Best scene ever. Everyone totally hates him afterward.

Fran: The Viera may begin as part of the wood, but it s not the only end we may choose.