Shanks is my favorite, not because he is strong, but becauase of his role in the story and how mysterious he is (or how Oda show him in the story).
Tbh, Shanks is a typical shonen character who is placed as a teacher/motivator and introduced early like Kakashi, Gojo, Urahara in Bleach, and so on.
Nothing special, but these types of characters always get intended reactions from the reader.