Nikon F — 1959
The Nikon F is historically significant (at least in photography). It's not the first anything, but it had that combination of things that made people buy it. It was so successful that it transformed Nikon from another Japanese maker of Leica-copies into a professional-grade player that could compete against the likes of Leica, Rollei and Zeiss Ikon.
This camera gave Nikon the 35mm pro market, which it had mostly to itself for the entire 1960s. It wasn't until Canon's F-1 came out in 1970 that Nikon had serious competition, and by then this camera was superseded by the F2.