Well to my mind, it would definitely be the legendary Frank Zappa.
"His work could be experimental, mind-bending, avant-garde—and so could his children’s names. But it’s his desire to pursue the lesser trodden musical paths, his outsider status, and iconoclastic music, that have ensured his influence on a variety of music genres like heavy metal, funk, noise music, classical, and the tradition of satirical rock songs."
(Holmes, 2012)

With his first album The Mother Of Invention - Freak Out Zappa created a full hour of pandemonium infusing intense blues, psychedelia interspersed with doo-wop and lyrics that singled out the flaws within the pop culture at the time; breaking any and all musical conventions at the time.
Zappa since went on to release another 61 (yes you read right) albums during his lifetime and in doing so changed the face of music forever.
To my mind, Zappa was an absolute nut, however his influence within the experimental genre has in turn forced society to re-examine its musical standards and pushed the boundaries of music to where they are today. If it wasn't for character's such as Frank Zappa the world might yet be stuck listening to music of the 70's; instead we have so many new and exciting genre's as well as sub-genres to broaden our musical variety.
Bellow lie some examples showcasing some of Zappa's more experimental compositions.
In conclusion then, the world would not be as musically diverse if it wasn't for pioneers like Frank Zappa, so thank you Frank, you shall live on a legend.
Reference Links:
http://thecreatorsproject.vice.com/blog/original-creators-avant-garde-rocker-frank-zappa