I am afraid of the dark...
...but only when it's sudden.
When I was little, I used to be afraid of the dark in general—I remember this very clearly, sneaking down to the other end of the house and sleeping at the foot of my parent's bed. Growing up though, I've forced myself to face my fears and now I absolutely love the dark. I love how thick it is, empty even—but only when I can control it.
If it's sudden, from, say, a power outage, I tend to experience anxiety and hypervenalate.