Nobody mentioned the Holga yet. The plastic piece of $hit makes some pretty interesting pictures, and is like a liberation army in escaping technical mumbo jumbo. Basically, aim, shoot, wind, repeat.
But I have never had a camera that scratched my film so badly, and needed so many modifications just to function. For example, the high tech foam that's supposed to tension both spools of film comes off in hot weather and gets wound up with the film on the take-up spool. A very interesting feature. I have to tape the back door with gaffers tape or it comes off mid-roll. I've had to polish the interior with the finest grit sandpaper I could find, and then use coarse paper to get it even finer, in order to avoid scratching the film along the film guide, and it STILL scratches my film (I had two of them do this).

So, I gave up, put one of the cameras in the street, and ran it over with my car. Felt great.

But, to me that is by far the worst camera design of all time. There is no comparison.