Also, not metal per-say, but I was listening to a Zero Karma album my mate recommended to me today and it wigged me the fuck out. It's described as 'ambient ritual', and it seemed all alright, pretty twitchy and voodoo until I discovered that ALL THE INSTRUMENTS WERE MADE OUT OF HUMAN BONES. It really changes your appreciation of a song when you discover shit like that. It's really creeping me out.
Zero Karma:
http://www.youtube.com/watch?v=0yVM1ttrtso