Most: spontaneity. Or at least being engaging and interesting. I like being surprised and captivated, especially if it's combined with a great sense of humor. 

Least: I don't really know. Arrogance, perhaps. And that's different from (over)confidence. That might sound funny coming from me but there's a difference between what I do and someone who genuinely regards others as inferior and acts snooty or sneering. I can't stand that.