A pirate whose sole goal is "NO MORE NINJAS!!!" and worships the one true FSM (none of this alfredo heresy)
Dread Pirate Roberts (from Princess Bride) - wear a mask, play a new character every few adventures, but they all call themselves by the same name and pretend it's always been one person.
Buccaneer - you actually work for a government, attacking ships from their enemies
Keep fish - have an aquarium in your quarters, insist an sailing to different lands looking for one more special fish, hang yourself over the edge of the ship with your head underwater, etc... Maybe you also cook fish, looking for that perfect dish.
You want a mermaid wife and you're going to get one, no matter how much time you have to spend on the ocean looking.
You're totally convinced you're descended from Neptune, king of the seas. The only weapon you'll use is the trident.
Good luck!