1. Passion, whether sexual or a great love of what they do.
2. (Justified) confidence. I admit that at times I mistake arrogance for confidence, but there is something sexy about someone who is spectacular at what they do and knows it.
3. Vulnerability. When a guy tells me something that I know very few, if no other people know, I find that it cements an initial attraction.
4. Thoughtfulness. A male friend of mine would always walk around to open the car door for me even in the pouring rain and always knew the right thing to say to make me feel better without sounding patronizing.
5. Intellectual curiosity. I like a guy who knows he doesn’t have all the answers but knows he can ask the right questions to get there.
6. Strength of willpower. It always seems that I want the ones who have told me “no” more than the ones who said “yes.” There is something to be said about the idea “The best sex is the sex you’re NOT having.”

My dozen, not in any particular order.
1. Maturity
2. Balance
3. Confidence about who they are, what they are about
4. Ambition and work ethnic
5. Generosity
6. Articulation
7. Responsibility
8. Decency
9. Hands
10. Eyes
11. Scent
12. Reasonable fitness

Alright, I’m going to write mine before I read the other answers, it is a little convoluted cause something’s are different with women than men, I’ll see if I can sort it out as I go.
1. Depth – being interesting is very much about being interested. The broader the context and experience and possible approach the more I seem to be intrigued.
2. Set point – Do they see possibility and beauty in life and people or do they see limits and flaws.
3. Do they get me, really get me… Can they appreciate the extent of who I am and what I offer?
4. Do they crave, seek, need deep human connection? How badly? Will the out it all on the line, make themselves completely vulnerable and open to get it.
5. Do they really understand and are they capable of true honesty and authenticity.
6. Desire for evolution resulting in quality or mastery or enlightenment in aspects of themselves and others.
7. Courage – I want to do things, not just want to do them, not just talk about doing them, not just read about other people doing them.
8. Confidence – grounded in themselves and their ability to learn and be resilient.

Crap gotta go… I’ll finish in a minute.

I really liked this Luis, ” thus she’s not begging for anyone’s attention.
These are features from people with strong personality.”