Shine by Mr.Big is the first song that comes to mind for me.
From the Hellsing series. I was a young kid back then when I first saw Hellsing and heard the song. I just wasn't interested in it at all back then. It didn't have the usual exciting beat/lyrics that I was used to hearing at the end of an episode.

As I sadly have gotten a lot older now 😅, thankfully my music tastes have expanded and I now appreciate this song a hell of a lot!

I hope you all enjoy