Eleskin,
you should be a bit more specific on what your budget is and what you are looking for, then it's easier to help. For example, for around US 500 you should be able to get Summicron DR, V2, or V3, or even the new Elmar (a great lens) if you are patient. Also, there are Hex 50/2 and Planar, of course. They all draw a little different but have high res. across the field.
If you want a special signature, I recommend a Sonnar variant, like Canon 50/1.5 or Nikkor 50/1.4. Will run you around US 300 or so.
Great and faster general purpose lenses are the Canon 50/1.4 and CV 50/1.5, for around US 250, used.
Then there is the Canon 50/1.8 for around US 150.
Many, many choices.
Cheers,
Roland.