Ok I know this website is supposed to be about 35mm cameras but it would would be remiss of me if I didn't at least mention 120 cameras. Medium format has been the premium film format for a long time due to its versatility and wide range of cameras and lenses that take 120 and 220 film.
I'll let you do your own homework but I had a long love affair with the Pentax 645 manual focus cameras and the later 645n auto focus cameras and lenses. Joshua Gull has done one of the best 645 camera reviews and comparisons, which saved me no end of typing....you can find it here. Excellent work Josh!! My personal favourite portrait lens in any format is probably the manual focus Pentax 150mm F3.5. The shot below was taken with it on Portra 160 and whenever I want to remind myself how good medium format can look I'll look at this shot.....an all time favourite.