Luffy

Luffy's most dominant traits are his apparent lack of common sense, his utter fearlessness, and his unwavering belief in himself and his abilities. He generally marches to the beat of his own drum, unwilling to approach anything in a delicate or nuanced manner. He emanates sheer confidence everywhere he goes, and is profoundly ambitious, frequently declaring that he will become the pirate king and devoting his life into being one.

Luffy's personality can be described as childlike, in the sense that he tends to go to the extremes. He can either be tremendously greedy, especially in cases of food, who his crew is, and adventure; or extraordinarily selfless, going so far as to virtually sacrifice himself to avenge or protect his friends, crew, and family. In other words, he never backs down from a fight, no matter how dangerous or strenuous it may seem. However, this childish mentality does not prevent him from often getting to the root of the problem and allowing him to figure out the simplest way of solving it. But beyond all, he never fails at maintaining a positive, carefree attitude along with a bright, genuine smile adorning his features.

An important side-note: Luffy acquires the properties of rubber, meaning he is unnaturally stretchy, after unknowingly eating a Devil Fruit.