I am usually never scared in the woods anytime day or night. However, once I was walking to my stand about 5AM and a Grouse flushed right beside me....now that got my attention!
Another time I was ground hunting and sitting on a rock drinking coffee waiting for first light. The buck I was after that day deceided to play "sneak attack" came in behind me and started snorting, and pawing.....I had to laugh afterwards... needless to say he busted me early, and I had hot coffee all over my camos.

Odd as it sounds although it has never really scared me, I agree with Coyotefeeder. Once in a great while, there are some spots that you happen onto while in the woods, you know somehow you are just not welcome for some unexplained reason. And that is a very strange feeling to have.