Exakta 500 - if we are talking design and not execution...
It's a nice chunky brick of a camera that fits the hands perfectly.http://www.cameraquest.com/exa500.htm
Unfortunately it has a bit of the FSU 'Tractor School of Design' about it, evident when you wind the film on and hear the gears having "workers' paradise contradictions." But, hey, you can identify the sound of each and every gear -- it's sort of an emotional connection with the camera.
I also thought the Miranda Sensomat was neat: A Pentax Spotmatic with a removable finder; the metering cell was in the mirror, a la the Topcon. But again, a triumph of design - Miranda's were not noted for reliability.