Hm, I guess I have no favorite character since during all of those years readin OP I kinda began to adore all of them. They are all unique and I must say that Oda did a marvelous job portraying their characters.
Isn't haki something like a spirit that the user is able to manifest in a form of an ability? Like being able to percieve or repell anything around them. That's how I see it anyway