Oh boy, am I glad that I found a site where I can tell others my bizarre nightmares and overall creepy dreams. And boy, can I tell you guys some good ones.
Well, y'see I have remembered most dreams I have ever had since I was roughly... 4 or 5 years old. If it was a particularly interesting one, I can withdraw it from memory and recite it to the tee and plenty of those have been nightmares. Now, I can't really say which one was my favorite, so I'll just randomly pick one from memory:

I'm walking through a house with my little sister. It's set up like a carnival attraction, yet something didn't feel right. There are no people in this house. It's completely devoid of any life what-so-ever. As we are walking through the house, the feeling gets worse and worse; until finally, a strange little girl starts walking through the room we are in. She has her head down, so that her auburn hair is over her face, and is sort of shuffling along a set path through the room. My sister turns away immediately and with a short squeak, and as I'm staring in fear at this little girl, she suddenly whips her head up, revealing a face that chills me to this day. This face is missing the eyes, and nose. A large black hole exists where those features should be, and the mouth...appeared large enough to be taking up half of her face. It didn't have sharp teeth or a long, snake like tongue. I think this was the thing about it that scared me the most, the bizarreness of the rest of the face, paired with an utterly normal mouth, albeit a large one.

This girl looks up at me, and starts to emit a strange, low howl-like noise. Then, at light-speed, she instantly gets closer to me, the howl now increasing in pitch. I close my eyes to make her go away, and I hear the howl go down. The shuffling continues and grows quieter and quieter until it's gone completely.

We continue going through the house as if nothing happened at all.

However, not long after we left that room, the shuffling starts up again, and I immediately close my eyes. The shuffling continues as I stare into the blackness, and once it's gone, I open them up again. When I open them though, I'm not seeing the room around me. I'm staring at the face of the little girl, close up. The howl begins again, and rapidly rises in pitch until it's a scream. The black hole that were once her eyes and nose get closer and closer until they swallow me up.

This was actually a recent nightmare I had. It scared the ever-loving crap out of me, so much that I didn't want to open my eyes back up when awakening from it for fear I would see that ghastly face staring back at me.
I have more that I can write down, but let me know what you thought of this one. This definitely isn't the scariest I've had though.