Top 10% - gets the coding job done, timely, high quality code. Knows his craft well, but is still essentially a craftsman.
Top 1% - Designs systems that will get the job done for the business/larger org goals, or even designing systems that generate business props. Also, the systems designed are capable of being implemented/maintained by lesser skilled developers. Of course, knows his craft, but is something of the artist, can see the Buddha in the gearbox.
The 1% guy should easily, as in no conceptual difficulties, be able to write a compiler/interpreter, that clearly demonstrates whether one is simpatico with the machine, capable of thinking like one. Actually should love doing this sort of thing, probably, and might have to resist the the tendency to incorporate custom command processing components/metadata/languages in every project.