Orlion took three of mine already...
Tony Iommi of Black Sabbath, Ritchie Blackmore of Deep Purple (He wrote the most famous riff ever, and the best song ever (Stargazer) Also I like nested parenthesis), ... whoever does the song writing in Judas Priest, Denis "Piggy" D'Amour of Voivod, Lennon-McCartney, you know, The Beatles.
For slightly more modern song writers there is Nico Wenner of Oxbow and for a lot more modern there Rosalie Cunningham of Purson...
EDIT: I almost forgot Mirai Kawashima of Sigh.