I have a Minox 35GT which fits in my front pants pocket next to my cellphone. The only caveat is that it's scale-focus (no rangefinder) and the exposure is by aperture priority (no manual or shutter priority settings). Originally I thought that a scale-focus camera would be too hard to use, but it's not. Because I've gotten use to scale focussing on the Minox I have been scale focussing on my Super Ikonta instead of using the rangefinder. Scale focussing to me is much faster than using the rangefinder, but there is a slight learning curve when you are getting used to judging distances which in itself is probably a good skill to have.
My Minox has a very sharp 35mm f/2.8 lens and I have no problems with it.