Over the past 50 years, I've worked with nearly all the film M models.
When I bought my last film M (about 11 years ago now), I chose an early-series M4-2. This camera has what is for me the ideal viewfinder (essentially an M4 viewfinder with the non-flaring RF patch and thinner, lighter frame lines) and the ability to take a winder if I so desired, as well as a hot shoe. It was in bargain condition when I bought it ($700 or so) at KEH, and needed the viewfinder/rangefinder to be cleaned, lubed, collimated, and calibrated ($100 or so at my local tech's shop). I almost always have a 50 or 35 mm lens on it, and it works perfectly.
The cost of camera, viewfinder service, and both Color-Skopar lenses (new) was well under what I've seen for even just a body in similar shape nowadays, so it was also one of the best bargains I've gotten over the years.
G