A couple of folks already said this one but dressing room of a JC Penny in the King of Prussia mall in PA. I was shopping for jeans and I kept seeing something in the mirror as I was trying on jeans. I finally watched the mirror while I was doing it and saw the guy in the next room peak over the wall at me. I finished trying on my jeans then looked over the wall at him. I ended up fucking him in the dressing room. This was years ago before bareback and when I was still versatile and so I tossed the condom into the storage room, the store was in the midst of a remodel.
Then there's all the usual places. ABS, Valley Forge Park, the old Pines area. The JC Penny is my best and most unusual though. Not had any action in a very long time, 10 years on Black Friday 2024.