I saw a "ghost" walk into my room when I was 7 or 8.
My room was about 15' x 15' and I was at the back corner with the door diagonally opposite me. It was really late and for some reason I woke up and was looking out my door. All of a sudden a lady walks in really slowly. I couldn't see a face, only the moon light from behind going around her body. She was the same height as my mom and it looked like she was wearing a night gown.
This was not a slight ghost image out of the corner of my eye. I was sitting in bed looking directly at her. I could see her walk. I could see her figure and everything like a normal person, but with a creepy silhouette like you get with a backlight and darkness.
She walked really slowly towards me. I could only see the outline so I thought it was my mom. I called "mom" in a quiet voice, but no reply. Each step she took I called again, but no reply. I thought it was my mom not wanting to answer and try to trick me. Each call, my voice got a little higher.
She walked very slowly to me and got within 6 or 7 ft from me. Then she started walking back out. I could tell if she turned around or just was walking backwards. I was freaking out somewhat, but still not sure. She walked out as slow as she came in and I watched her back out the door.
At the time no one was in the house but my mom and me. So being a curious little bastard, I got up to see if it was her. The whole time I wondered if it was a ghost or her, but despite it looking like a ghost, I thought it surely was my mom. (I was a rational kid)
I walked out my door and into my brother's room where my mom went to bed that night. As soon as I looked in, I saw hear in bed, snoring. Instantly I went from rational to WTF!!!!!! I knew then it was a ghost and screamed really loud.
The dog on my mom's bed woke up and ran after me, biting and attacking me. Here is was, rolling on the ground, beaing attacked by a dog and shitting myself over a ghost, knowing I had to go back to my ghost room to sleep. My mom woke and was also like WTF are you doing. I tried to explain, but to her I was just a kid with a ghost story.
As I write this I have goose bumps. But, I am still rational. Just because I saw a lady or ghost, there might be another explanation for a figure appearing, that is within science, that we just don't understand.
EDIT: I changed 15" to 15' since I don't live in a shoe box. Good catch