OK for those who LOVE FF10s, it is simply called "Decisive Battle" as far as I know. There's no debating that 10s is THE most complicated. Man I freak out when I hear that song! But I am a firm lover of FF6 and 7s (Orff or not lol). 8s sounded a little cheesy but GOSH that beginning is soooo touching with the piano and harp type thing going out. Necrons in 9 was pretty awful, but "Dark Messenger" was amazing (which is odd cause they're kinda the same style).

As for non-last boss (since I'm on a roll lol) THE number one for me goes to "Fierce Battle" from FF6. Then the Jenova themes, then "Legendary Beast" (FF8) after that, just about any old Boss music is amazing. Ummm would I be hated by adding in that Chrono Cross has the best overall soundtrack followed by Legend of Mana? The Gloaming there's a sweet little last boss ditty. Sorry if I went off on an uncalled for tangent, but that's what I do!