50mm - f1.4: Big aperture standard prime, and more $$(Sony version selling $699)
50mm - f1.7: Slightly smaller aperture, but cheaper in $$(below $200)
50mm - f2.8 macro: As the name, a good macro lens. Up to 1:1.
All of these lens are very good on their own. Produce very nice pics. With 1.5...