Wow, I must be pretty cynical, I have a much easier time coming up with deal breakers that key traits I'd actually want in a partner.
I guess someone who is going to give as much to a relationship as I do, which is a lot, and someone who is going to fight for me. Not literally pick a fight over me, but fight to be with me, even when things rough. Also, I'd expect him to stand up for me if his friends or family are saying mean things about me, as I'd do that for him.
Beyond that, honesty, caring, mutual respect, blah, blah, blah. Everyone needs those in a relationship.
I've never met anyone who said "Boy, I hope my next girlfriend lies to me, that's such a turn on."