That guy has to be my favorite black metal vocalist ever, and the band in general one of my favorite bands, because it gives BM a dose of the ferocity it often lacks. Now, V.I.T.R.I.O.L. aka Dave Hunt's vocals span a lot of different styles, but what interests me most are his insane screams and shrieks. They remind me of a rabid, lycanthropic crow, and this crow's last strand of restraint has been broken, and it is ready to rend flesh with its cacophonous beak.
Any other bands with such vicious, unhendered screams?

!T.O.O.H.! has some of the most insane harsh vocals you'll ever here. Plus, they're awesome.

Seconding !T.O.O.H.!. I actually posted a thread similar to this a while ago, let me see if i can remember anything.... Alan Dubin's vocals are pretty fucked up, and you can see them either in his drone metal band, khante, his grindcore band, O.L.D., or his Industrial/Doom Metal band Gnaw. Also if you just want pure strange vocals (I personally don't like them all that much, but its still starnge as hell.) Then check out the vocals on Fleurety's "A Darker Shade of Evil" EP. The person who did the high vocals messed up his vocal chords to the point where he couldn't sing anymore. Just listen to it, ive never heard anything else like it.

Dark Tribe's "In Jeraspunta" has some of the most insane, disturbing vocals I've ever heard.

I'm not too familiar with Anaal Nathrakh, so I don't know exactly what you're looking for, but some of the most insane (literally) vocals I've heard are from the Russian NSBM band Moloth (aka M8l8th). Specifically, the first album (possibly the live album as well, though I haven't heard it). The second album seems to have a different vocalist.

I'd say Lord Worm is pretty crazed.

You may like some Bethlehem, specially their second album, Dictius te Necare

Verschleierte Irreligiosität

I find V.I.T.R.I.O.L. and Jason Mendonça from Akercocke to have a lot in common, vocally - gut-wrenching death metal gutturals, ear-piercing black metal shrieks and some of the most amazing cleans in metal, period, nowadays.

And there's also Attila Csihar, but that goes without saying. Anaal Nathrahk are a purebred Mayhem worship band, anyways. And I mean that with utmost respect.

I couldn't imagine anyone who wouldn't like Mortum. Some fucking tortured sounding, insane, maniacal vox. Great band.

http://www.youtube.com/watch?v=hIxzk6K7 ... re=related