FFI: Final boss (Chaos) theme
FFVI: Dancing Mad
FFVII: Those Chosen By The Planet
FFVIII: Man With The Machine Gun
FFIX: Necron Battle Theme (even though he sucked for a final boss :p)
FFX: A Contest Of Aeons (Summoned Beast Battle)
FFXII: Esper Battle

Havent really thought about II-V yet or the spinoffs and I dont play XI