First off - hell yeah I watch One Piece! I'm only up Enies Lobby, so I've got a long way to go, but I love it so far. Anything with that kind of vibe to it would appeal to me. I actually was in the One Piece RP going on at the minute very briefly, but I had to drop out early on due to illness. Still regret that.
Other than that, my time on PC has mostly been spent in Pokemon Trainer Academy. I enjoy it mainly for the character development/interaction, since it doesn't have a solid plot. So I like anything that lets me explore characters, their journey and their relationships.
I'm intrigued by the idea of your RP. If it was something I got into I'd like to know all about the other characters before making my own - I like to figure out what the gap is and help fill it. No point in making the meathead muscle guy if there already is one, no need for a ship engineer/shipwright if there already is one, know what I mean?