Here's one of the programmers I respect most who I will guess only a few here have ever heard of who falls into this category:
Since that conversation with Neil some years ago, I have interacted with Tom and read his mailings on the postgresql mailing lists a number of times. There, you see him dealing with all the usual bullshit everyone has to put up with in real time: toolchain regressions, build farm issues, niggles in two features that interact badly, and so on. Besides that, the quality and care in even the first draft of his features are also remarkable.
Unlike some famous programmers who -- while very competent -- can be very contrarian in their work (and invite controversy, which is some form of self-promotion), Tom is not as such, and I think provides a great counter-point to that style of distinguishment.
I think it'd be fascinating for someone who has the skill to interview him about his long and productive service to writing useful software. If I have to guess on his behalf, here's what I can assess about Tom:
* Work on important problems
* Work on them for a long time each
* ...but not necessarily forever
* Build the software to last
* Keep working