I'd go all Pentax for that =].

Seriously, here is a quick rundown. All my opinion so take it with a grain of salt.
Pentax ME- smallest and lightest. Aperture-priority only (no manual). Surprisingly likable camera.
Pentax ME Super - A bit heavirr than the ME. Manual available. Some dont like the push buttons to select shutter speed but never bothered me. Some common mechanical issues.
Pentax MX - all mechanical version. reported to be more reliable than the ME super. (I dont have one myself)
Pentax Super Program / Super A - a tiny bit larger than the ME/super but with a very nice grip and larger viewfinder. My favorite of the bunch.
Pentax K1000 - All mechanical, reliable, but more of a medium-size camera with more of a clockwork feel to it.

Olympus:
OM1: mechanical, reliable, small, but sturdy feel.
OM2: electronic, reliable, good manual mode, heaver than the ME's. *One thing I would like to mention is the extremely easy exposure compensation knob.
OM10: low-cost version. manual adapter available, reliability issues.

**Both Pentax and Olympus share some qualities as a system.. They are compact, reliable, and deliver excellent results. You can easily get a basic kit of a camera and lens(es) for a low price. However if you want more exotic stuff like super-wide angle lenses, super telephotos, and extra bright lenses, be prepared for a steep price curve and low availability. However there are more aftermarket lenses available for Pentax.