Mark Bass, the director of instruction at Willows Run Golf Academy in Redmond, is a great golf instructor.
It is worth noting that in all sports, a great athlete does not make a great teacher. You could have Tiger Woods himself come in to teach you, but I doubt that he would be a better golf teacher than David Leadbetter, for example.
With this point in mind, I would like to say that Mark Bass is a great golf instructor. He completely reoriented my golf swing around body weight transfer rather than arm power. He also straightened out my swing plane, which helped my accuracy tremendously, especially on the short irons.
What makes him a great teacher is that he has that unique ability to look at your swing and tell you what you're doing wrong, and what you need to work on to improve it. He also covers course strategy in his instruction, including what type of shot to play when, and course management skills.
If you are at all interested to pick up golf, or lower your handicap if you already play, I would wholeheartedly recommend Mark as an instructor.