I think the thing I've hyperfixated most on throughout my life is Super Smash Bros.
When I was a kid I played Brawl endlessly and even now I go through hyperfixating on it from time to time.
I've hyperfixated on just playing the game and having fun, the subspace story mode, youtube videos of Smash bros., Smash bros machinima, making my own massive Subspace-like story with all the characters in Ultimate, Smash Bros esports (for my school), and even Amiibo training. And Smash bros is the reason Nintendo as a franchise and the history of the company is such an interest of mine
I haven't hyperfixated on it in a little while but I'm sure it'll get back to me eventually. It's only a matter of time