The K-1000 was a very popular all-manual SLR camera that was one of the longest-produced cameras in history, brought out in the late 70s (before any SLRs had autofocus) and finally discontinued around 1997. The demand for this camera is still huge and the only reason Pentax dropped it when it did was because of the plethora of these cameras on the used market.

The K-1000's claim to fame is that it does everything it's supposed to do easily and with no surprises. (The fantastic metering setup doesn't hurt either.) They're also built like a brick, you couldn't tell a heavily used one from 1980 from one from 1995.

The K-1000 was so popular that there seems to be no more than six degrees of separation between someone who has used a K-1000 and another. I own one myself.