There used to be a huge overweight (500+ lb) guy who would go into the only handicapped stall in the building and go to sleep for 2+ hours at a time. You would clearly hear him snoring. It was very weird.
The most uncomfortable place I've ever shat is at a state park right before a triathlon. For some reason, nerves always get the better of me at those events, and about 20 minutes before the start, I must take care of business or I have abdominal cramps for the entire race. Anyway, this place had 5 concrete wall stalls, with no doors, opposite the wall of sinks (and mirrors). It was high traffic, due to the large number of competitors, and the only way someone could tell if anyone was in the stall was to walk by and look. Also, it had the cheapo toilet paper that you can see through.