On a crop sensor I guess you will be looking at 50-85mm? I could recommend the usuals:
Super Takumar 55/1.8, 50/1.4, 85/1.8, 85/1.9
Carl Zeiss Jena Pancolar 50/1.8
Meyer Primoplan 58/1.9
Vivitar 85/1.8 (rare, but lovely smooth bokeh)
A cheap option would be the Pentacon 50/1.8
If you want something that glows wide open:
Chinon / Reflecta / Yashica / Revuenon 55/1.4
Meyer Triplan 100/2.8 (soft wide open with crazy bokeh)