Bowman. The guy often went against conventional hockey wisdom. Wasn't much for line-matching or consistent linemates. He was tough, occasionally gruff and very demanding. Having met the man and talked with him for a few minutes, he'll never be confused with the best personality or the best talker in the game. But somehow he was an excellent motivator. He was a brilliant tactician and strategist. His teams were always well-prepared. And despite his faults, he was always able to get the most of every team he coached.
After Bowman, my list would likely be Toe Blake, Al Arbour, Fred "The Fog" Shero and Glen Sather. Tommy Ivan, Jack Adams and Punch Imlach, even though their coaching style is very old-school, would be up there. I wouldn't rate Roger Neilson in the top 10, although I firmly believe he deserves to be in the HHOF. As much as I like Cherry, Harry Sinden was a better coach.