Someone had to ask.
My fav fight for Sanji has to be the merman one. I'm reffering to the anime.
For Zoro it's against Mr.1 and Luffy.
For Chopper it has to be against that knight in the skypiea arc. That and that's the only one I remember cleary.
Usopp has to be against Luffy.
And Luffy is the one against Croc in the ruins and Eneru.
But out of all the fights it's has to be Luffy vs Croc in the ruins. Both anime and manga