Personality wise?

They have to be able to engage in small-talk that will build into meaningful conversations. Asking me about the weather's nice, but be able to take it further. It means a lot to me, like you're actually thinking through what you're saying to me beyond a statement or two. I like having one on one conversations, the time spent on me.
They have to be witty. Dry wit, sarcasm, I don't care. Just be witty and we'll get along smashingly. They have to be able to make me laugh.
Self-confidence. Oh my God that can be great in the right amount. Too much and I'll threaten that they're choking on their own dick, and too much I'll think they believe they don't even deserve one.
They have to make good apologies. Not just a simple "I'm sorry," that doesn't cut it. There's a methodology to apologies. Saying I'm sorry is easy, meaning it is a lot harder.
Compassionate. Being sweet on me is nice, but being kind to those around you, and giving a shit, now that's something. There is more in the world than what goes on past our doorstep, and recognizing that, and trying to help everyone else be better? That is a turn on.
Tolerant. Lifestyle, religion, music, personality quirks, a tendency for bad days... All of it is amazing. It makes me respect the person, which is extremely healthy for any relationship.
Dog lover. Counts as a personality trait in the Sims, so why not here?

EDIT: Does personality cover being able to keep secrets? If so, that's important. I don't want someone spreading my shit everywhere.