For me, it was a third world gas staion in West Virginia. It still haunts me.....
EDIT: My Story
Basically was on a road trip driving through WV at about 1 am. The pain strikes and I get off the main road and locate a "gas station" which was supposed to open 24/7. I run inside and find the "restroom". Upon entering, it looked like something out of some type of apocalyptic movie, true third world country kinda stuff (peeling paint on the yellow walls, god knows what growing on the floor). 2 stalls, 1 urinal, 1 sink. The first stall had a door which was only hanging by the top hinge. Upon opening this little slice of heaven I discovered the bowl had been used quite frequently and from the looks of things, had backed up long, long ago. I backed out of stall and made my way to stall two, which had no door. Upon entering I noticed the seat was askew and had enough hair on it to comb and style. I was at the break point though and had no other option. I pulled down my pants and contorted myself into a spiderman like pose in the stall, hovering about everything. About half way through, the door to the men's room opens, and the gentleman who runs the establishment starts walking in and sees me, in my spiderman pose, hanging from the stall walls, a couple inches above the seat. We make eye contact, and he turns and walks out. A couple minutes later after I finish and basically speed walk past the counter and out the door.