Whats good bro?
Im into the same kind of stuff. You can usually find great samples just by listning to any opera/classical/orchestral. Carl orff is good stuff, the track "o fortuna" was actually used in hate me now by nas, and countless other songs. I hope someone could help you with artist more than i can.

People usually define that errie hiphop as "horrorcore". IF you like that stuff def check out Gravediggaz, The Flatlinerz, Headless Horsemen, even Jedi mind Tricks. Can't think of anymore of the top of my head. Necro and Sutter kain are usually grouped into that whole genre as well