One day, sitting in the throne room of your evil, black skull fortress, a bunch of androgynous teenagers kick in the door. They're brandishing swords about the size of motorboats and claims that "your days of evil evildoing is over". You calmly get up from you chair, walk down towards the group of insolent little kids(and an old dude with sunglasses), smirk, and snap your fingers. The floor around you fall apart, forming an arena surrounded by lava filled with radioactive deathsharks. [Insert your weapon of choice here] suddenly appears in your hands, and background music starts playing as the fight ensues.
Or, well, the above scenario is how I'd design my black fortress of final boss-ness. However, the important part is the background music that starts playing here. What would it be? Do you have a specific genre, or even a specific song, that would start playing as you'd destroy the only people stupid enough to attempt to end your schemes of [insert morally questionable plan here]? Let us hear which ones, and why!
My choice, for the moment, would be G5 Project - Machinery. The intro is seriously one of the best boss-fight intros I can think of, and the rest of the song, consisting of pretty damn good instrumental heavy rock, would fit the entire fight fairly well. Also, it's badass.