The basement library washroom at my university was notorious as a place to crank one out during study breaks. The walls of a few of the stalls were always covered in cum. It was especially hot to see an athletic good looking guy walk out of the washroom and then find a wet load dripping down the wall. It made great lube to add my own load to the wall.
My fraternity had a huge collection porn magazines floating around and it was always fun to find a wet load in the pages. We all know why some stuck together but a still wet one was a special treat.