IMO the best Manual Focus camera is the one that is working with film in it and a lens on it and within easy access.
By that definition I do not own the best manual focus Nikon, but depending on my mood tonight, it could be either a Nikon FA or FM, right now the best Nikon I own is my N90s.
Beyond that, they all have unique switches and doodads that do some such strange function that 99% of the people that buy them may never use, or a knob or toggle is in just the right place for your hand. Lets face it here, these are high quality cameras we are talking about here, in that regard they are all the best. When you find the one that works best for you, then you have the best MF camera makes for you.