Hmmmm
I have a few pretty niche kinks (like tooth brushing) but I understand why they're niche and not very popular so I can't say they're necessarily underrated. Maybe tickling as an aspect of BDSM? It rides the line between pain/pleasure and its wonderful to utilize within power dynamics. Exposing your vulnerable, sensitive body parts to someone's mercy knowing they could torment you any moment by tickling you. It's almost like a form of torture where you recover near instantly as soon as they stop.

As for overrated.... daddy dom/little. It's everywhere 😭 no shade to those who genuinely enjoy it, but it's so pervasive sometimes it almost seems like THE thing people think of when they think of kink. Also not that into puppy play in the way its usually done. I prefer the humiliation/dehumanizing type of pet play more than the animalistic, embodying the essence of the animal type pet play that seems more popular