Since I unfortunately can't afford a Leica (or a Contax G2 for that matter), I wanted to ask you guys which non-Leica rangefinder I should be looking at.
Some years ago I asked myself a similar question (I would have loved to try a Zeiss Ikon ZM - but it's too expensive for me and will always be) and my solution was the aforementioned Contax IIa / IIIa.
I use to take them both with me (for coloured and black-and-white slides) as soon as I'm travelling and don't want to carry around heavy stuff. Those two bodies with four Zeiss lenses 35, 50, 85 and 135 weigh just about 2 kilograms.
It's a
real pleasure to take pictures with this gear. Almost anything is possible.
Despite what some posters above have said, it's shutter on a properly working example is whisper quiet in my experience - not quite a Leica M3 in the that regard, but close to it.
My postwar shutters sound exactly like this. They are even more quiet than a friend's Leica M2 shutter. We have compared both.
But: there is a
huge difference between postwar Contax IIa / IIIa and prewar II / III shutters.
The postwar shutter is pretty quiet, especially at slower times like 1/25, 1/10.
The prewar shutter of my Contax II is really loud, even like the shutter of my Contax RTS II SLR if you fix its mirror. At slow speeds like 1/10, 1/5 and 1/2, it gets even louder

.
One time last year I took some portrait pictures of a good friend in a café. It was a disaster because I had brought an SLR with a winder. That was really noisy. Sure, its 85mm f/1.4 Zeiss lens was beautiful. But I wish I had brought one of my quiet Contax postwar RFs with its 85mm Sonnar instead - my friend and me, we both would have been
much more comfortable

.
Sad to say the Leica M3 - and Zeiss' inability to develop it further - left the Contax RFs behind.
Especially with regard to the rangefinder itself - the 1951 Contax IIa rangefinder looks like the Contax II rangefinder from 1936. I think this is
the weak spot of the classic Contax RF cameras. Especially when you have to wear glasses.
Fortunately, there are additional Zeiss Ikon "Universal" finders (prewar and postwar) for wide-angle, standard and telephoto lenses which are definitely useful.
As for the Zeiss lenses - I've just developed some black-and-white slide films from last year and sometimes I cannot say anymore if I took a picture with my (coated!) Contax RF lenses or with Zeiss-C/Y-lenses. So even my 70 or 75 year-old Contax RF Sonnars and Biogons, Zeiss-Opton and Carl Zeiss Jena, do an excellent job.
There are also uncoated Contax RF lenses available, mostly prewar ones from Carl Zeiss Jena: They do have a certain kind of charm, softness, sometimes almost a little bit of certain poetry

.
I would not like to use them
only - but I've just developed a slide taken with my uncoated 50mm f/2 Sonnar which I enjoy a lot.
It just depends on the light situation. I would like to experiment soon with these uncoated lenses using a Fujichrome Velvia 50 which is well-known for producing intense colours.
Michael