Awesome Characters Film Franchise Headscratchers Main NightmareFuel Trivia YMMV
The Chronicles of Riddick
Riddick himself. Something about a remorseless killer that can see in the dark and says things like "Don't worry about what I do for you, worry about what I'll do to you." scares people. Not sure why.
The Ghost Drones from Dark Athena are arguably this, as well.
How about the Necromongers? Join them, and you experience unimaginable amounts of pain. Refuse them and die. Escape them, and they'll destroy your planet (Which they were just going to do anyway).
Dark Fury has Antonia's idea of "art". Get frozen into a living statue, aware of everything that is happening to you as you stand there posed for what may be hundreds of years. Antonia mentions that it can take a full day's effort for her "art" to blink.
Quite a bit of the first movie could be applied here, given the whole "Horde of monsters lurking in the darkness" bit. Sure, they could be repelled by light, but that only holds out so long... and you can only point lights in so many directions.