The K-1000 is a lovely, simple, and rugged SLR. I have only one complaint: it is a “noisy” and perhaps slightly imbalanced camera. When you press the button that shutter/mirror combo is like firing off a gun, and the camera shakes noticeably. A bad thing for slower shutter speeds.
I was always very fond of the Olympus OM series bodies and the Nikon FE body.
There were a lot of great cameras made by Nikon, Canon, Pentax, Minolta, Konica, and others during the golden era of film SLRs, but IMO the best was the Olympus OM series, because designer Maitani started with the goal being an SLR and lenses which were small and light. The OM could do almost anything a pro Nikon could do, but cost less and was much less of a burden.