back when I got my first cheapo sampler, and still thought that looping a sample was cool, the first thing I sampled was Hand Of Doom off Paranoid - I can't believe no one has rapped over this ever, seriously funky shuffling side-stick shizzle (a la Al Green I'm Glad You're Mine etc) with slightly atonal/blue note bass progression.
Fantastic song too, about a Vietnam vet's descent into heroin addiction, with pioneering use of the [quiet bass-only verse / exploding guitar shred chorus] effect (well exploited by Pixies/Nirvana/etc 15-20 years later) with Iommi's trademark horror guitar stab overdubs a la War Pigs.