I think I made a thread like this before, but why not redo it? Lord Worm on None So Vile takes my vote because of the various types of techniques he uses. Inhales, exhales, and that odd pig squeal during the slam on Slit Your Guts.
Hmm... Frank Mullen in either Effigy of the Forgotten or Pinnacle of Bedlam.
I honestly enjoy his vocals on Effigy of the Forgotten. Everything after that doesn't appeal to me.
Also : Jason Peppiatt Scepter of The Ancients is pretty fucking awesome.
Glenn Benton on Deicide's debut, Peter Tägtgren, Mikael Akerfeldt and the guy from Gates of Ishtar on The Bloodred Path.
The guy on Dark Millennium's Ashore the Celestial Burden has my favorite vocal performance, although they aren't really death metal vocals. Otherwise, van Drunen on Consuming Impulse.