Most of the fixed lens rangefinders from the 70s are good... provided you find one in good condition. elekms questions are good ones. I'd also add 'how important is size' and 'how comfortable are you with doing some repair yourself'.
I've been on a mad rangefinder buying spree the last few months (if I can find something interesting for under $20, I have a hard time passing i up!).
My go to rangefinder is still the Canonet 17 GIII. It took me a few tries to find one that wasn't jammed/had a stuck shutter and I had to do some cleaning/rangefinder adjustment when I got it, but the camera is nice. Compact, fast lens, workable meter, etc.
I like the FED 2 for the interchangeable lens capability, but it is a bigger camera. Not huge by any means, but it isn't quite as compact which does change how and when I use it.
To be honest, I haven't come across a flat out 'bad' rangefinder from the 60s-70s yet (ignoring broken ones). All of the Olympus rangefinders seem like solid cameras though the 35RD usually has stuck shutter blades which need some work. The Canonet is my default recommendation because they seem so plentiful. The Ricoh 500G mentioned earlier is also nice, as are the Yashica G line (though there again, you are back to nearly SLR size cameras).
I found this site rather useful:
http://www.cameraquest.com/com35s.htm
Again though, for me, the compact size, image quality and manual control were key features. Your values may be different.