This occurred when I was about 6 years old and I was with 2 other neighbourhood kids. The weird thing is, I have never been certain as to whether this was a dream or real. I can recall one of the kids confirming this story, but then denying it later. I do know that, if it was a dream, it occurred in two parts and included the part with the other kid confirming it. It also sounds similar to other stories I have seen on this site.
One day while playing in my basement, two friends (B & L) and I encountered what appeared to be a man or man-shaped thing who was totally black and hairless. We were in one end of the basement and the thing approached us slowly. I can't remember our initial reaction or when we first noticed it, but we started throwing toys and cardboard boxes at it. It just batted them away easily. It got about ten feet away and one of us threw a larger box at it. The strangest thing happened: the box opening landed over the thing and it seemed to disappear into the box. The three of us wasted no time to check, bounded onto the very large toy chest to our left and ran across it to the stairs and out the door.
I don't know why, but later that night, just before dinner, I went to the basement to check the box. Stupidly I was alone. I went over to the box, curious about what happened and picked it up to check under it. I immediately found myself standing directly before the thing, again at its full height. I ran upstairs with the speed of a panicked child and screamed for my mother. She didn't believe me, of course. I don't know how long it was before I would go to the basement again and I don't think I ever felt comfortable there again alone.
I never saw the thing again, but I remember talking about it with B & L and we had (as kids will do) theorised that it can from the place where the chimney ashes were swept. We figured it was made of ash!
Anyway, this incident has haunted me ever since and I don't think I'll ever forget it. I still plan to find one of those old friends and ask them now what they remember.