AlexanderCao I feel this is a bit too basic, and wouldn't leave much of an impression. If I describe myself, for example, I'm a 21 year old college student studying computer science, and as hobbies, I enjoy writing novels and reading manga. Was that memorable? Okay, let's go further. I have brown hair, green eyes, a knack for engineering, and a taciturn nature in person. Was that any better? In my opinion, no. After all, I'm only telling you what I'm like. Sure, maybe the dichotomous nature of my hobbies and profession (humanities vs sciences) is interesting, but beyond that, none of this leaves much of an impression.
Tomoyuki I agree. What you said is spot on, since what makes a character memorable isn't some shtick or unique trait, but how that trait plays into the overall plot. Though I'd like to add that the most important thing is how the character's personality, past experiences, and relationships with other characters change them, or those around them. Let me give an example:
I love Oregairu, the abbreviation of the Japanese title, "My Youth Romantic Comedy is Wrong, as I expected. The main character, Hikigaya Hachiman, is a pessimistic, seemingly self-centered yet self-degrading high school student who made love, life, and the illusory goodness of "youth" his enemies after a confession gone wrong. As he meets people, most notably his counterparts Yukinoshita and Yui, his selfishness collides with his self-degradation, and he finds himself throwing himself under the bus for other people, apparently because it was more efficient to do than through any other means. Whether it was playing the villain in a nasty spat, or showing a hopeless romantic that they didn't have a chance at their crush by literally confessing to the girl himself, he ruined his own reputation for the sake of others, all because he simply didn't care.
This, in my opinion, is a solid example of a memorable character. The dichotomous traits Hikigaya possesses, coupled with his relationships with others, are what makes him shine.
So in essence, what I'm trying to say is the characteristics of a character aren't what makes them memorable. It is, as Tomoyuki says, how it plays into the plot, and more specifically, the interactions, decisions, and choices brought about by those characteristics.