What are the most attractive qualities in someone?

What do you find yourself falling for in a person/what is your type? Also, why do you think those qualities are attractive? Do you think this person is realistic or are they more based in fiction?

Personally, I prefer people who are serious and composed. I just like them to foil my personality so we both stand out more, if that makes sense. Since I'm outgoing and cheerful in real life, I'd like someone who could keep me grounded, or in other words, tell me to shut the hell up. Lovingly. Anyway, I'm curious! Let me know!