I don't know how I ended up in this page... I'll post my opinion on One Piece ships nonetheless, for the main ones at least.
Sanji x Nami:
Eventhough romance isn't the focal point of Oda's storytelling, I think this is the most likely and most developed romantic relationship in the manga. I reread the manga many times and I noticed that if you pay close attention to the interraction between these two characters, ignoring the obvious gags, it's like a mini romantic boy meats girl story. So I hope in the end of Once Piece they end up together to conclude ther mini arc of a story, otherwise the clear developed tension between the two, expecially in the last two arcs would have been added needlessly by Oda.
Sanji x Pudding:
These two has some chemestry, being two talented cooks, however I don't see them ending up together. Eventhough it started as a forced marriage between the two, Pudding ended up infatuated by Sanji by the end of WCI arc, and by then, I thought that maybe there's something that could develop between the two, however Sanji did something unexpected and ignored her infatuation with him on multiple occasions, which was a first for him. It was as if Oda was telling us, the readers, that he didn't return the sentiment. Still, with her present feelings for him I thought there was still some small chance for them to end up together in the future, but when Pudding kissed him and then erased his memory it was dead deal by then. It symbolized her letting go of her feelings for him and marking the closure on their relationship and the end of their little mini arc.
Sanji x Viola:
There isn't much to say about this pairing as it wasn't developed much. All I can say is that there is some attraction from Viola towards Sanji, but it ended as just that as there wasn't any further interraction between the two.
~These are the three possible pairings for Sanji that I noticedd so far.~
Zoro x Tashigi:
Just like for the Sanji x Nami pairing, these two has the second most developed tension in each of their interractions. As I see it, if Zoro was going to end up with someone, there's no better than a swordswoman.
Zoro x Hiory:
This one is new so there isn't much to talk about. We'll wait and see how their relationship will develop in the future, but for now it's to a lesser degree similar to the Sanji x Viola situation.
Zoro x Perona:
These two spent two years living together alongside Mihawk so there may have been some romantic development between them in the background, though so far I don't see any. In contrast, there was some interesting interactions, however small, between Mihawk and Perona. So if there is a possible pairing then it'd be Mihawk x Perona for me.
~These are the possible ones for Zoro for far~
Luffy:
As a main character, Luffy could literally be paired with any female character that he had interacted with so far in the manga so it's difficult to choose one from them. For his part Luffy didn't show even the slightest inclination that he was attracted to anyone in particular as all his interaction has been brotherly in nature. However there were some females that showed clear interest in him so I'll only include them.
Luffy x Hancock:
This is an obvious one as Hancock is clearly hopelessly fallen for him. I could see them ended up together in the end but for now it's still onesided attraction. Luffy has rejected her marriage proposal many times, however contrary to Pudding who put a closure to her relationship with Sanji, Hancock still wasn't deterred in her pursuit so their status is still open to change in the future.
Luffy x Alvida:
Alvida is the first female in the manga to show romantic interest in Luffy. I'm not intirely sure but I think she's also the only one that Luffy complemented on her beauty in the intirety of the manga. However, eventhough I think Oda first thought of her as the possible future love interest for Luffy, I think he forgot about her by now or possibly changed his mind and replaced her by Hancock due to the similarity in their characters that's centered around beauty. Even her attraction to Luffy wasn't mentioned or even alluded to in the manga in a long time so as I see it the possibily for them ending up together is very very small. She may even be by now Buggy's girl for all I know.
Luffy x Rebecca:
Contrary to the previous two, Rebecca for her part doesn't show romantic attraction toward Luffy but she has great admiration and respect for him which sometimes could translate to attraction. That's the only reason I made her a possible pairing for Luffy. She's a similar case to Vivi as they're both princesses of a country that Luffy saved, though there's a major difference between the two. Vivi has admiration and respect for the entirety of the strawhats not just for Luffy like in Rebacca's case. That's why I won't include Vivi in the chosen pairings for Luffy. Not to mention the existance of Vivi's childhood friend Kohza that has more of a chance to end up with her. However the possibility is still there however small it is.
~These are the main ones for Luffy that I see~
Fanky x Robin:
Eventhough I'm not a great fan of it, there are many clues that alludes that there's something going on between Franky and Robin. However I could objectively say that their personalities complement each other very well, so i could see them ending up together at the end.
Usopp x Kaya:
This is a very obvious one so I don't need to say anything about it.
Chopper x Milky:
She's a female mink deer that Chopper was infatuated with, so if he was hooking up with someone in the future there's no better match for him.
I won't comment on the following pairs but I chose them depending on their little interractions so far:
Smoker x Hina
Sabo x Koala
Sai x Baby 5 (This is a canon done deal)
Brook x Panties (Lol)
