Those fireball-throwing "imps"(although they looked more like wolfmen) from the original Doom still scare me. There's just something about that hissing noise they make and the gross sizzling sound when you get too close and they start frying you at pointblank range.

The split-face dogs and nurses in Silent Hill 3 were terrifying for different reasons. The dogs could just leap from the darkness and take a bite out of you. You always knew when the nurses were there because you can hear them breathing, but don't see them until they're almost on top of you.

And I liked the SH movie. It was easily the least bad VG flick I've ever seen. The acting isn't perfect, but they captured the look and feel of the series extremely well.