Canon A-1. The Canon A-1 is very gimmicky, long on distracting flashing red lights and multiple AE modes, while short on real useability, such as not having any metered manual mode, and having a very stiff shutter release, and that horrifying Canon A-series "squeal." The plasticky feeling Canon FD lenses also were none too appealing.
Pentax MX. I really wanted to like this one, as the idea of having a small camera like my beloved OM-1 cameras, but with more advanced Gallium metering cells made the MX seem appealing. However, I found that the MX's shutter action is very unrefined compared to the OM-1, having a good deal of harsh, undampened vibration and being a good deal noisier.
On a more positive note, I just got a new to me black Nikon F2A. Always wanted to try one, but wasn't sure it would live up to the hype. The F2A I received looks almost new, is very clean and smooth, and its meter readings seem spot on. I always thought it was a very large camera and was somewhat surprised to see that it is noticeably smaller than a Nikon d750 (a modestly sized DSLR), although the F2A feels quite dense, and that the F2A has very little vibration to go along with its wonderfully crisp shutter release and shutter sound.