My forgotten camera is a Voigtländer Perkeo I, a pocketable 6x6 folding rangefinder that I bought at a flea market for a couple of bucks. The lens is a 75mm ƒ/4.5 Vaskar. Focusing is a matter of guesstimation and a fair number of my pictures have been out of focus. The camera probably needs a CLA. I eventually bought a Yashica Mat, which I found to be a lot easier to use but doesn't really count as a forgotten camera (or is this just my opinion?).
The picture I have included was taken in Middelburg, Holland. I remember being surprised at it when I hung the film up to dry.
I'm looking forward to seeing what others submit.