I think this is a very personal answer of what I seek out in a developer:
Ability to communicate effectively. This means the ability to communicate his/her ideas through code, ability to communicate his/her ideas to other team members, ability to work well with other team members, etc.
Passion for learning and improving
Passion for writing good, maintainable and scalable code
Ability to learn fast
Independent thinking
Enjoys tackling problems that he/she has never come across