Bought via eBay a Nikon 50mm f1.2 AIS lens. I already have a Nikon f1.8 AFS lens -- which takes fine photos -- but wanted a fine manual focus 50mm with really shallow DOF, that I could also use on my Nikon FM3a and FE2, as well as my Nikon F6 and Nikon D750. Just barely managed to resist total GAS fever by avoiding bidding on Olympus OM Zuiko 40mm f2 and 50mm f1.2 lenses for my OM cameras (which I still use).
I also bought a Nikon K3 type focusing screen (split image/microprism) for my Nikon D750, to make manual focusing with that DSLR easier (it seems OK with the stock screen, but there is definitely room for improvement). Supposedly, the screen will not interfere with the focusing points, gridlines, etc. that appear in the D750 viewfinder.