Like most (all?) of you, I own plenty of cameras - Leica screw mount, Contax, Nikon digital, Rollei, Hasselblad, weird ones, and Leica M's. When not shooting professionally, I switch back and forth among the cameras, primarily to see if I 'see' any different/better from one camera to the other. But, I always seem to come back to my M2 - it seems to allow the ability to shoot quickly, frame easily, and catch/create the moment that often results in a great shot - much more so than any other camera I have.
If I only could keep one camera, my M2 would be it.