Im big shipper, so i wanted to join the conversation and share what i feel about One Piece couples.
It's implied that Smoker and Hina know each other very well in any sense. So, to me, it's more than a ship, they are almost a canon couple.
There are people shipping Smoker with Tashigi, but i see them more as a father daughter relation.
Sanji x Pudding. I also see this one as an almost canon couple. I think Oda really went far with this couple. The interactions between these two ruled the wci saga. Sanji with Pudding can express the best of himself, and on the other hand Pudding act with Sanji in a similiar manner that Sanji act with other women. They fit each other so well.
I ship Zoro the most with Robin, but he is also a good match for Nami due to their hot and cold relationship (with both of them, they had way more interactions in pre time skip, when Oda used to care about develop the personalities and the relationship between the straw hats). I actually feel like most of One Piece girls has a little crush on Zoro, but he is annoyed by almost each one of them. Zoro see in women something that is weak and must be protected, but his bond with robin is built different, Robin is not something just to protect, she is also someone he can count on.
So the main reason i ship Sanji and Pudding and Zoro x Robin are very similiar:
Sanji interacts with Pudding in a new, mature way, that is different than the attitude he showed with all the other female characters. I think everyone can agree with this. Zoro interacts with Robin in a respectful way that is different than the "must protect this annoying girl" attitude that he has with all other female character.
I ship Luffy, Franky, and Brook to nobody actually, but i understand people shipping Luffy x Nami and Franky x Robin, since Oda use to push in that direction. Even though Luffy and Nami are shipped probably mainly because they are Male and Female protagonist, so of course they share many moments together.
For some reason i ship Monet x Law and Mihawk x Hancock, both couples would be cute together, and also Zoro x Perona has their cute moments.
Hope someone can relate, ty for reading :)