Having something pop out and you jumping is not scary. Being afraid of what might pop out is scary. Penumbra. I got to the spiders and quit. Also, the game has some cool puzzle elements utilizing physics and real world knowledge, such as Morse code.
Spoiler & Protip: Dogs can't reach you when you are atop a rock or similar raised platform. But you can reach them. Dogs become a lot less scary when you can just bludgeon them from afar.