Home alone one night in my apartment. I always locked and dead bolted the door when my husband was out, so when I heard a knock on the door around 10 or 11 I ran to let him in. With my hand on the dead bolt, something told me to stop and look through the peephole. A man in a ball cap stood there--with his hand over his face. So awful to think what might have happened if I had simply opened the door.
Edit: Sorry guys, didn't realize anyone wanted details. Blatantly hiding his face. His whole head was turned to the side and down, flat palm up against the side of his head. No clipboard, pizza, uniform or anything like that. I backed away from the door (ugh, I can still feel what it was like to be separated from him by only a few inches) and yes, he eventually left with no further trouble. In retrospect, should have told management about the shadiness.