The Pentax Auto 110 Super has the reputation as "the world's smallest SLR, in 110 format." This camera is part of a well developed system which includes several lenses, flashes, autowinders, and accessories. The film compartment is indexed to read either 100 or 400 ASA 110 cartridges. There are still a few film options available, and some people even cut down cinema film and hand load the emulsion. I've only shot one roll of Fukkatsu 400 color so far, and it was a blast. The Fukkatsu is super grainy and yields some interesting results.
The Auto 110 Super has a spacious viewfinder with a split screen and micro dot center prism. It is very bright and easy to focus under normal lighting conditions. It has an AE Lock button, self timer, and operates in full auto mode. The camera is often available in a kit which includes most of the prime offerings. Here is a link with more information about this amazing little camera: Classic Camera Guy- Pentax Auto 110 Super