What songs just scream final boss? Have you ever listened to a song and just thought "DAMN! This would make an awesome final boss track!"

Not only am I asking what songs would make awesome final boss tracks, but I am also asking in which battles these songs would play.

I've got to say Mozart's O Fortuna would make the most awesome final battle song of all time. My friend heard it for the first time on Friday. He asked me what game it was from. I told him it was Mozart and he said he'd never heard it before. Now actually designating O Fortuna to a game would be a hard thing to do. The song pretty much would fit into any final battle. It has chanting and almost sounds religious, so I'm saying it would work in a final battle with an angel in it. I've got to give O Fortuna to FF6.

Here's another:

Prince's 1999 to the final battle with Lavos in Chrono Trigger.

One final one:

Beethoven's Moonlight Sonata to second Time Devourer from Chrono Cross.