A Kodak Retina 1a. Beautifully built and as it doesn't have a rangefinder, inexpensive for a Schneider lensed camera. Not the fastest camera to operate but pretty compact folded even by modern standards.
..... and a Retina 1a here as well for £20 in an antiques barn. As blockend says, very compact and a feeling of being very well made. The shutter makes a beautiful noise, though it strains the ears to hear it!
A little Penti I. No rangefinder, no meter, just lots of faux gold and 30 half-frame exposures per film.
The thing I love most about this camera? People don't take you seriously... try street photography with one of those big black things and you'll see what I mean. With this camera, people just smile and think it's some kind of toy... And besides, for 5€ you can't go wrong