Mine are the Hisuian balls, specifically the Hisuian ultra ball. I just love the design of the latch, and the color palette used for all the balls. I especially enjoy the little flourish on the yellow stripes of the ultra ball!
What's your favorite? Any particular reasons why?
It's supposed to be a mechanism like a suitcase or chest latch.
Now that you've said zipper, though... I can never unsee that. 😂
EDIT: The master ball is iconic. It's not that I don't like it, I just don't use it. Not out of some RPG-esque "but what if I really need it later?" kinda thing, I just... prefer not to use it.