Last night as I was refilling my water bottle for the night, I looked out at the sitting room window, and was practically overcome with fear that something was going to come through the window. It didn't take me long to get over it, not anywhere near as long as when I wake up after a nightmare, or two nights after seeing Blair Witch and hearing noises outside.
Say what you want about Alien vs. Predator - Requiem, but it had several scenes that stick with me. The worst one in my mind is when the little girl calls for her dad to say that there's a monster outside her window. The dad goes and looks and out of the complete darkness a xenomorph almost fades in, seen only by the shine on its carapace and teeth.
That is my kind of fear.
Especially outside the dining room which is shaded from the light on the walk. At night it's really dark, and I can almost see someone hiding on the other side of my reflection. That's why that curtain remains pulled at night.
At least this is a describable fear. Even some in dreams or nightmares make sense: the shark in the giant indoor swimming pool; the bear in the woods behind the house. Then others are less tangible: the free moving silhouette with glowing eyes, the large-skulled dog that makes everything go black and white, and whose laughter I hear in my head. The worst are the ones that make no sense whatsoever, and yet are terrifying in the moment, like three baboons on mini-bikes in a Chinatown market.
Keep that one form tweaking with your brain.