DSC0570420140323ILCE-7 by
jenkwang, on Flickr
Jupiter 8 (50/2) at f2.8
I like this lens, dunno if its king or not (considering its price, more like "pauper"

)
The Sonnar look with rounded OOF highlights (and aperture) for very little money.
Rounded aperture for a cheap 50mm is not so common on the 50/2 Jap lenses as most of those were considered 'cheap kit lens' and often had fewer blades to keep construction simple and cost down, even when they can be better optically (ie. sharper)
Almost like a mini J9 in how it renders, but with a shorter FL and associated working distances.