I also prefer mine with a personal injection of "hell yeah, let's finally get the big bad" adrenaline.
Sigma Fortress 1, Mega Man X
Solemn, somber, yet determined. Pumps you up but not in a cheesy way - shit is real and you are about to finally take down Sigma for good, and the music conveys this perfectly.
And this SHOULD have been the final level in Battletoads Arcade, The Dark Queen's Battleship:
Everything I said about Sigma Stage 1 applies here too. But this is stage 3, despite The Dark Queen being the big bad, and this being her literal fortress... wat. It's the final stage in my heart.
What are your favorites, and why?