There are good products from all of the major manufacturers and other companies as well. I recommend getting something that was a very respected camera at the time and constructed with some durability. If you get an older totally consumer camera I think you are asking for more trouble. My personal experience is with Pentax, Olympus, and Nikon so I will stick with those. Others will be able to chime in about the good choices from Minolta and Canon.
I think that the Pentax MX or K1000 are good choices. Both are manual exposure and there are a bunch of good lenses to choose from. The K1000 is more of a student camera and lacks some of the features of the MX and is also larger. The MX is very compact and is a full system camera with motor drives, backs and other accessories available. Both seem to be very reliable.
As for Nikons, there are many choices, but I will mention the FM and FE series of cameras. These are excellent and were used as backups and even primary bodies by pros in their era. The FM and FM2 are manual and mechanical cameras. The FM2 has a newer shutter with faser sync speed and top speed. The FE and FE2 are aperture preferred auto cameras that require a battery for the shutter to operate, except that the FE2 has one speed at which the camera may be fired with no battery. The FE2 has the faster shutter and also adds TTL flash metering. The lenses for the Nikon are also incredible, of course. My experience is that they tend to be a but pricier than other brands, but in this day and age, they are definately affordable.
The Olympus OM1 and OM2 cameras would also be good choices. They are very compact and have a wonderful line of compact lenses. The OM1 is mechanical and manual whereas the OM2 is electronic and has aperture preferred automatic exposure. I would suggest looking at the newer versions of these cameras, the OM1n and OM2n. I would probably suggest not looking at the OM2Sp, because it is a very different camera with more potential reliability problems.
Have fun and good luck!