Old abandoned ruins in some woods and heard Barn Owl noises. They were positive they had proof of a haunting or monster (whichever they were hunting for). I was roflmao, because they had no clue. Another favorite "weird" sound for out in the woods are Barred Owls. They can have extensive "conversations" among several of the owls, some close, some very distant. Sometimes they sound like monkeys, others strange humanoid voices. I swear that at least one of the "Sasquatch" recordings is barred owls.
http://www.youtube.com/watch?v=b3Li74LzXCk&feature=relatedhttp://www.youtube.com/watch?v=92Dst0T1fzU&feature=related