I've heard quite a few of these stories, especially the hanging dog one at the beginning of the thread.
Also heard one about wishing on a monkey's paw that turned out to be cursed.
Another one about a girl who had only a ribbon which prevented her head from falling off 
Stick men, if they exist must be aliens mustn't they?? Anyone know if the first picture on the thread is 'real' with children and the slender man in the background?
I've read some really scary stories on a paranormal website - the one that stuck in my mind was this one:
'Ghoul on the Swing
by Amber
It was summertime in 1992 and I was about 15 or 16. Having received my learner's permit for driving, my mother had taken me out to County Line Road to practice. This is a long, straight country road that divides two counties in Northwest Indiana. We had driven this road many times before, as it was a family tradition for a Sunday drive.
On this day, I was at the driver's seat. I was driving along and we were immersed in conversation when I felt a chill. The hair on my arms and the back of my neck stood straight up and I could feel my heart pounding in my chest. My mother had stopped talking and I could tell that she was feeling this as well. I continued to drive, and slowly (as if forced to), I turned my head to the right, my mother did as well. As we looked out the window, and a small, yellow house came into view. I felt fear like I've never known before.
As we continued, I noticed a tree next to the house with a swing. And sitting on that swing was a man. I call him a man because that is the only way I can describe it. He wore all black, including a black derby hat. I remember that I started shaking when I saw his face. He was looking at us and following the movement of the car. His face was red and disfigured. He was smiling at us as he swung. I swear we locked eyes. My mother and I never took our eyes off of him. It felt like it took a century to drive by this house. Then I started crying. My mother started crying. We both looked at each other and said, "What was that?" It felt like Holy Fear.
Having reached the end of the road, we were forced to turn around and go past this house again. Although this time we knew it was there, we were still not prepared to be totally paralyzed with fear and forcibly drawn to it again. But we were and the tears began to flow again. This time I felt my mom snap out of it and heard her utter a silent prayer. We drove away from that place shaken. We still discuss that day, and even talking about it or thinking about it continues to give us physical reactions.
As an adult, I drive by that area quite often now, but I cannot seem to locate where that house was.'