I've owned and used almost any kind of RF camera so far, I could easily say that I love more (with no particular order):
1. Iskra (I wear spectacles and it is still easy to frame and focus)
2. Retina IIIC (The smallest camera with no compromises ever)
3. Leicas M (M6 & CL)
4. Yashica 35 CC (useful lens focal length and reliable automatic exposure)
If I had to keep just one then I would keep them all, or maybe with a gun on my head the Iskra (it gives better image quality among the four).