The Best Screenwriting Teacher

I thought it might be fun to get opinions on the best screenwriting teachers out there and why. I know Syd Field gets slammed a lot these days, but I think what he's tried to teach still holds plenty of merit. Of course there's Robert McKee, who certainly must believe he's the top teacher and perhaps he's right. And how about John Truby, Bill Martell (an actual produced writer), Richard Walter, William Froug, Lew Hunter and many, many others? There are so many out there now...

Any thoughts on who the top teachers/authors are?