Ophie
Salingerian Phony
I think Pyukumuku is the breakout "cute" Pokemon of this gen.
I like it, but I think the real breakout ones this time were Mimikyu and Alolan Vulpix. Then again, that also depends on your definition of "breakout," considering Mimikyu was marketed a lot and Alolan Vulpix has a major role in the anime.
Pyukumuku is one of my favourite Alola Pokemon. It's cry alone does it for me. I really need to EV train one even if it's a terrible Pokemon in battle. It's just too cute to not have.
I always have the sound on when I do the Pyukumuku chucking just to hear its cry over and over.