Um, yeah. Hands down, one of two things. The girl from the Ring crawling out from under my bed/out of the TV, or thinking about the movie The Strangers. I haven't seen the movie, but I have had countless dreams/lie awake sessions thinking about creepers breaking into our house and torturing us! Usually, in my nightmares, they're dressed like police officers.
When I was little, my fear was the boogeyman! Not the actual, scary boogeyman, but the clearly costumed "Mr. Boogety" from the Disney Channel Halloween special.
What about you? Nighttime fears – from childhood and now?