Kurt Cobain and Dave Grohl are awesome.
What about Otep?! She's pretty good. Her voice is dynamic. It shows in her reproduction of nirvanas' Breed.
Corey Tailor seems to have lost it a bit in Slipknot. But has improved with his other band Stone Sour! Gavin Rossdale from Bush was pretty good, so my friend tells me. I have yet to judge myself