When I was five or six years old, I was spending the night at my grandparents house. They had no pets, and no access to the house for an animal to get inside.
I've always had trouble falling asleep right away, and I remember just lying on the couch in the living room waiting to fall asleep. All of a sudden I heard what sounded like a small dog barking in the distance, outside of the house. The sound of the barking came closer, and closer. Then I could hear claws clicking on the linoleum flooring as it ran through the hallway from the kitchen into the living room where I was lying. All of a sudden the dog was on top of me licking my face, and being very rambunctious. I remember feeling its breath on my face as well.
It felt like a small dog, and appeared to be very friendly. However, since it was invisible, I was scared and tried to push it off of me. It finally jumped down, and I could hear it run off the same way it came in. After about a minute, the whole episode repeated itself. I remember telling the dog to go away and leave me alone. After the second incident, it never happened again.
I don't remember mentioning the occurance to my grandparents the following morning, but as long as I live, I will never forget the invisible dog that came to visit me.