Small, lightweight, and simple. They viewfinder can be more illuminating of the whole scene than an SLR.
They take a bit of practice to master the zone system and the patch alignment. RF's are considerably less flexible than an SLR, but they are quick and easy to use.
I second the list above with my comments. A Yashica GSN is also good, if on the large side. I very much like the Olympus and Canon 35mm series. Ihave the Oly 35 RC/2.8 and it is so small and light it goes anywhere, with the slight drawback of a slower lens. The Yashica 35 GSN/1.7 is big but is dead simple to operate and has fantastic glass. The Canon QL17 is a very nice, solid RF with very good glass. Only knock on it is it does not meter in full manual mode.
All of these can be found for less than $100, and there are very good places for a CLA for all 3 brands. Others will chime in with other brands and recommendations.
Thanks for the info. Now I need to do more research on each of the listed RF and find the right one for me. Appreciate all the comments!