Well, as far as Original One Piece OC's go - I never really had particularly many until I started RPing. I enjoyed the idea of someone who would mimic any of the father figures Luffy has, so every character I dreamt up was some variation of (what extremely little we knew about them at the time, 15-18 years ago) Shanks and Garp. 

My original RP character was a Marine Commander by the name of Kai, 13-14 years ago. Edgiest Marine OC you ever once did darn see. Six powers, big fat Mihawk Black Katana he claimed rended the enemies souls - long before the infamous "This is Katana, her sword kills the soul of the people she kills" but most notably he wore an all black Navy coat that had "Death" on the back. It was all truly terrible and these days I'm very glad that [@Pacifista] rejected me from his One Piece RP back on Oldguild when I applied the the game he was running.