The Olympus OM single-digit cameras are the best I've tried. All have very large and bright viewfinders. The drawback is the view can be almost too large if you wear glasses due to the short viewpoint so I would recommend the OM-3 or OM-4 as they have dioptric adjustment and allow you to use the camera without glasses. The later OM-4 and the titanium versions are the best bet due the reduced battery consumption on these models. I have heard the 2-13 screen is the best though these seem to be as rare as hen's teeth.