I remember hearing a singer singing black metal style that wasn't metal. But I can't remember who though.
Attila uses central asian throat singing and I suspect so does the guy from demilich. If so, the guy from demilich is a great throat singer. I've never heard someone produce the tones he does. Either way, most death metal vocals are a variant of throat singing done unintentionally. I came upon this realization when I was learning to throat sing myself and noticed the similarities in the two styles. I learned to modify my throat singing to be more breathy and to only amplify the lowest harmonic and the result was a really low growl that resembled that of many familiar death metal vocalists. However, the singer from demilich uses a more pure form of throat singing so it should be distinguished from death growls.
EDIT: Does the singer from demilich really sing into a toilet bowl or was that a joke. I was wondering how huge that guy was to produce those low tones(throat singing depends on resonance in your throat, chest and mouth, hence the bigger you are, the lower the tones.).
I personally don't like Varg's singing in a few of his songs. He overdoes his voice making it seem ridiculous. It just sounds like an annoying whine and almost ruins the songs. However, when he does it right, his singing is amazing and definitely one of the best.
Perhaps a thread on singing should be started. People should post samples of their singing and they can be given pointers. Help can even be given to people wanting to learn.