Tough question, there's so many that I could mention. I dont really have one favorite but one that comes to mind is Christian Älvestam. He's probably most famous for having been the original vocalist in the swedish Melodic Death Metal band Scar Symmetry (when he left the band they ended up replacing him with two vocalists, which while not necessarily an indication of his level of skill is a very fun fact imo) although he's a prolific musician and has been involved in numerous projects.