Nuclear Throne's true final boss music (Not saying the name of the track because spoilers) from well... Nuclear Throne (soundtrack by Jukio Kallio). I also like Lil Hunter's theme (The One They Left Behind) and the credits song, Kings and Queens of the Wasteland.
I could cheat and say the entire soundtrack for Crypt of the Necrodancer (main soundtrack by Danny B.), but if you want a certain song, I would suggest Voltwaltz from Amplified
That's all I got. Sorry if you were looking for things not from games, but these are all I got