I'm using Nikon rangefinders, and based on lenses available, I'm missing the 28 which I had and sold, since I have CV 21, 25, and the Nikon 35, the 28 wasn't used enough to keep.
I also now have the ability to use my Vivitar Nikon F mount 19mm 3.8 thanks to Amedeo Muscelli's Nikon S-F adapter, and am hoping to find other even wider lenses that can be used with it as well.