I housesit for a family friend when she goes out of town. The woman who lives there is really into a bunch of spiritual stuff - new age stuff, reiki, etc. The very first time I was housesitting, I was outside watering the plants. I was the only one there and had closed the door after me. From the driveway where I was watering, I had a completely unobstructed view of the front door, the only door that was unlocked at the time. When I went back inside, there, on the little table next to the front door was a half eaten cookie. The table had been completely clear when I went outside and I hadn't seen cookies that looked like that anywhere in the house. Nothing too creepy, but very puzzling and unsettling.
When the woman returns, I mention it to her and she laughs and says she "gets ghosts all the time." I'm a fairly skeptical person, but honestly, ghosts were the best explanation.
The next time I was over, I was pooping around 10:30. The house itself is fairly old and creaks from time to time, but nothing too loud or disruptive. While I was pooping, there comes a single loud knock from the other side of the bathroom door. This wasn't a little creak or pop from the house, it was a loud, determined rap on the door. It was enough to scare my poop back in for the rest of the night.