Justin Hawkins =-=-= Learning from the likes of Freddie Mercury, Robert Plant, David Coverdale, and others Justin is the ultimate student of rock royalty. His falsetto is the absolute finest (and highest for a male singer) in the business and he has such commanding control of it.
Freddie Mercury =-=-= Need I say anything?
Axl Rose =-=-= Despite a good number of people hating Axl and his voice I think he is hands down of my the most unique sounding singers of all time. He has such a catchy grit to his voice that works to great effect in huge hits like "Welcome To The Jungle" all the way to and through "November Rain".
Meat Loaf =-=-= The big man with the big voice. Despite the ups and downs in his career over the years Mr. Loaf has sang his lungs out the whole way. His voice is so grand and powerful in all of his songs that it sometimes gives me chills. And unlike other power singers who have lost their glory with age (Elton John, Roger Daltrey, etc) Meat Loaf still sounds great.
Ian Gillian =-=-= Often credited as the highest belter Ian Gillian introduced no holds barred high octave screaming to music and could do so flawlessly live (as evident on "Made In Japan").
Honorable mentions: Brad Delp and Mike Patton