Im not really wild about rap music. Im usually more of a rock/metal man myself.
But.........Ive heard of Necro. Not really bad, beats the shit out of trendy Nelly type bullshit.
I actually like ICP to. Havnt listend to them much latley.
If your into that type of music check out horrorcore.com.(dont know if posting links to other boards is "legal" or not)
Anyway. Its a board for underground "death rap" as you put it. Most of them like to describe it as a horror movie on a cd.
Check out Q Strange and Sutter Kain. Brutalness.
http://www.youtube.com/watch?v=nTVPLeQvXNQ
http://www.youtube.com/watch?v=aewOSh98ir0