First Luffy: I prefer Luffy with Nami. I know it's mainstream, but i like them togheter. They're cute. And I don't say that because they're kinda the male and female "main-character". I also like Luffy with Vivi. But this couple is difficult, because she's a princess and he's a pirate.
Zoro: Oh god, I love Zoro and Perona. I know, it …..maybe won't happen... But it's to cute xD Perona is a little bit selfish, but she acted so sweet on the island (forgot the name) where they was stuck on together. I also kinda like Zoro x Nami ..but my love isn't enough to ship it. And I prefer shipping Nami with some other people. Is there any other couple? Zoro and Tashigi. It's cute too though... but i don't think they match up togheter... I don't know. Im not sure.. Maybe Zoro x Monet.... MAYBE.
Nami: I really love Nami. She is so cheeky and also cute xD Nami x Luffy, Nami x Sanji and i also like (a lil) Nami x Zoro ... and Usopp x Nami too. To Sanji x Nami: They match up. He really cares for her. Yes, he does that to all other girls too. But it seems like he would care for the others not as much as for Nami. Peoply always say, there is no chance for SaNa, because Nami hates him. But that's not true. I think she likes him too. But she doesn't show that and I can understand her at this point. If there is a guy who cares so much for you and tells you he loves you, then it's a great thing. But it's NOT, if he does that to EVERY second woman too.
Usopp. I like Usopp with Kaya or Nami. But I'm not sure....
Law... I like Law with Monet. Point. :D
Ace - ... I have no couple for Ace ... But Ace x Vivi is cute though.
To Luffy x Hancock and Robin x Zoro:
Those both couples are so mainstream xD ... I don't like them. Hancock is to old for Luffy. I like Hancock, but i don't like seeing her with Luffy. And Luffy said he won't marry her. So that's it. He'll never end up with her.
And Robin is to old for Zoro too. Yeah, they're both badass... But I prefer Franky x Robin. Oda said by himself, that if the Strawhats are a family, Robin and Franky would be the parents.