Real world the 21/4 and 25/4 Nikon Rangefinder Nikkors are practically impossible to find, and far far too expensive to use when you do find them. Even so the Nikkor 25/4 is a jewel of a lens, even if the finder is very mediocre. see
http://cameraquest.com/254.htm. The high Nikkor prices make your only super wide vintage choice the excellent 21/4.5 Zeiss Biogon in Contax RF mount in the $900/1000 range. Beware of the Zeiss 21 VF. It sucks. Use the super and inexpensive Voigtlander 21 finder.
The black Nikon Rangefinder Nikkors are much lighter and more pleasant to shoot with then the chrome, and so are worth the extra premium. The 35/2.5 black Nikkor is easy to find, the 35/3.5 black surprisingly rare, and the 35/1.8 sought after. The problem with the Nikkor 35's to me is that they are too close to a 50, so the only 35 NRF Nikkor I ever carry is the 35/1.8 for its speed. The black 28 is harder to find and more expensive than the chrome 28, but worth looking for.
ALL of the classic Nikkor wide viewfinders are MUCH inferior to the Voigtlander viewfinders. All of the classic Nikkors are not as sharp as the modern multi-coated Voigtlander lenses of similar focal lengths, yet they do have that vintage "classic" look if that is what you are aiming for. Unfortunately the Voigtlander SC lenses are discontinued and are now on discounted closeout. Once sold out prices are sure to go up due to user demand. Other than the 50/1.4 for the S3 2000 and the 35/1.8 for the SP 2005, they are the only modern lenses ever made in Nikon Rangefinder mount.
The widest lenses EVER for NRF cameras are the Voigtlander SL 12/5.6 and 15/4.5 in Nikon F mount, usable on the classic Nikon F and Contax RF bodies via the Voigtlander FS adapter. Scale focusing, but you don't need RF focusing on lenses that wide. see
http://cameraquest.com/VCSL1215.htm
My own favorite camera collectible is Nikon Rangefinder. I got started by borrowing $700 to buy two mint SP's and six lenses which unexpectedly stared me in the face from a local throwaway paper while I was having coffee in a tiny little out of the way California mountain town.
Stephen