My great-grandma told my mom this story:
During WWII in Germany, my great-grandma and her family lived in a nice house way out in the country, their nearest neighbor was about a mile away. Her brother, my great-great uncle was in the military before the start of the war, and was somehow distantly connected to the Valkyrie plot, so they shipped him off to the front lines in Russia. One night, the whole family was gathered in the family room, listening to the radio, reading etc. When someone knocked at the door. Surprised, they went to answer. No one was there. An hour later, someone knocked again. The looked, no one. So (i forget who) someone went outside to see if anyone was there. There was no one, couldn't have been kids, it was almost midnight and they lived far in the country away from schools. It happened several times before they went to bed. The next day, a letter arrived informing them that my great-great uncle had been killed the previous night. My mom likes to think it was him coming to say goodbye.
Also, in that same house a few years later, they were again gathered in the family room. They had a great big german shepherd with them. Suddenly, they heard footsteps going down the hall, and the dog started barking madly at the hallway entrance. Then it stopped at the entrance, and the dog whimpered and ran away. Creepy