I'd add a few things I've noticed over the years. Great developers like to pair program on tricky stuff, because they always learn something. They will try 2 different implementations if they're not sure which is best, and then the right one will then be obvious. They back their arguments with real world proofs. They try most fringe/new technology, even if it's not right for the current project. They hold large amount of domain knowledge in their heads. They admit when something is twisting their brains, draw it on paper, talk about it and then bang it out. They fantasize about what-ifs, in a perfect world, scenarios. And they love to share knowledge.