If you have the money the Zeiss ZF 1.4/50 Planar is probably he best high speed 50mm in F-mount.
The Nikkor AIS 1.4/50 is a close second, but I feel the tonality is not as nice and it has a little more low level veiling glare.
The Nikkor-S.C 1.4/50 delivers the typical high resolution / medium contrast look of it's era. I'm very fond of this lens, but would not use it as my everyday shooter. Some of these can be found in AI mount.
Ironically the Nikkor 2/50 is probably the best all around 50 in F mount. Sharp at all stops, flare proof, excellent tonality. And they are cheap. I'm particularly fond of the Nikkor-H.C 2/50. You can get these in AI.
The Micro-Nikko 3.5/55 is brutally sharp. Maybe even too sharp. From what I remember it delivers over 100 lines across the frame. Bokeh is a little weird and the signature can be a little harsh. Again, check that it is at least AI.
Just for the record, I own all of these lenses have shot them extensively.