Too hard to name just one, as there's so many different types for different styles and I like them for different reasons!

A few that spring to mind - Bruce Springsteen (Bruce Springsteen), James Hetfield (Metallica), Axl Rose (Guns N Roses), Sebastian Bach (Skid Row), James LaBrie (Dream Theater), Phil Anselmo (Pantera), Mikael Åkerfeldt (Opeth), Freddie Mercury (Queen) Meatloaf (Meatloaf), Bruce Dickinson (Iron Maiden)

Out of the above, I'd be TEMPTED to lean to Seb Bach for POSSIBLY my all round fave, because he has an amazing voice, with amazing range/power/diversity, and he's an all round perfect hard rock/metal band frontman!

But for the same reasons, so is Bruce Dickinson! And Metallica wouldn't be MEtallica without James Hetfield's immense voice, likewise Gun's N Roses wouldn't have worked without Axl, etc etc...