Tidus: I'll be right back!
Rikku: You're mean...cruel! Your moms would be ashamed of you!
Wakka: "Boom! Like happy festival fireworks, ya?"
Rikku: "You can cram your happy festival, you big meanie!" -Rikku

At macalania travel agency speak to auron
Tidus: I know, be prepared, anything can happen
Auron: Precisely
I don't remember what happens, but Tidus calls Auron old, then Tidus says "What?! I was just being honest!"

I'll add more when I think of them.