The Legend The Acclaimed BillyD!
Great one on one or in the tutorials. He knows his stuff and he can explain it very well and in an understandable way
Lectures on the other hand is a different story. With Bill you have to make sure your up to date with all the basics from the previous courses because he flies through complex problems under the assumption that you know what you should do at that point. Of course if you don't it means hard times ahead. So be prepared with BillyD.