i'm into mostly metal and i apprecciate people who pioneered any art form..a riff would not even be a riff with out some of them..so i am going to tonni iommi ..black sabbath (the godfathers of metal) influnced by the beatles and jazz etc. started a whole genre of gloom and doom(wierd)..of black sabbath because with out him in the begining i would of never cared about a riff..and alot of others as well..