50mm focal length is tricky to use well. I have used a number of 50mms across a few makes, and a number of 50s on my nikons. since most people of mentioned the good lot of them, I want to throw out the under dog, the 50mm 1.8 E series. I had a great many shots with that one. Mine had super loose undampened focus, and not the best feeling klunky aperture ring, but boy did it shine when it was needed. it was a nice compact package, and was coated (maybe multicoated?) Makes it hard to judge a book by its cover in this case.
The older 50mm 1.8 AF nikkor was also a sweet little lens that performed very well. though not built for manual focus.