I have three fixed-lens Voigtlander viewfinder/rangefinder cameras, all of which have normal lenses (Vitessa-L 35mm--50mm, Perkeo II 6x6--80mm, Bessa II 6x9--105mm), so no choice to be had with those.
On my Tech V 4x5", I have four cammed lenses (90, 135, 150, 210), and my favorite is the 135/3.5 Planar, because it's so sharp and fast (in 4x5" terms at least), and it's a good focal length for rangefinder use, since the viewfinder can be a little imprecise sometimes and there's a little more DOF than with a longer lens. On the other hand, I probably use the 150/4.5 Xenar just as often, because it's small and will fold in the camera.