[korphaeron]

1. Devin Townsend (Strapping Young Lad, Devin Townsend Band) - influential figure in music. Great guitarist, vocalist, songwriter and is the best frontman i've seen live. Ever.

2. Mike Patton (Faith No More, Mr Bungle, Peeping Tom, Fantomas, Tomahawk...) - Pure genius. If anyone makes me want to form a band, it's this man. I haven't seen him live, but I know he would be get to number 1 if I had. Best voice ever.

3. James Hetfield (Metallica) - Amazing live, great songwriter, sound musician and can still make a crowd go wild at 40.

I can't really decide any others. I love so many frontmen, but I couldn't whittle them down like I did there.
Mentions:

Chris Cornell (Soundgarden, Audioslave)
Layne Staley (Alice in Chains)
Zak De La Rocha (Rage Against The Machine)
Phil Anselmo (Pantera, Superjoint Ritual)
Simon Neill (Biffy Clyro, Marmaduke Duke)
Dave Grohl (Foo Fighters)