You could try Toriko- they've done a few crossovers. There's also "Fairy Tail" which I've heard described as One Piece but with magic instead of pirates.

hunter x hunter is the best of that genre but the author , togashi, is taking a break right now naruto is good but not as good as one piece, plus its over bleach is pretty good honestly im not a fan of toriko and i gave up on fairytail a while back as it became very lame and repetitive