Guitar has changed a lot over the years, and one of the most important pioneers in bringing about the rock n roll guitar is Lester William Polsfuss, or more commonly known as Les Paul. Aside from being an amazing blues and jazz guitarist, he also is credited with popularizing the use of signature guitar effects such as delay. Without him, rock music would certainly not be the same.
Jimi Hendrix is arguably the most well known guitarist of all time. Hendrix is accredited with popularizing the loud style of rock filled with effects and noise. Not only that, but his dressing style and stage presence was so influential it has lasted through the ages and can still be seen today.
Guitars are capable of a whole lot of sounds, and Tom Morello knows it. During his time in Rage Against the Machine Tom has crafted guitar solos that have been so creative you'd have no idea where the sound was coming from. Tom is a terrific example of breaking barriers and being original through music.
I love Jack Black. He started off as the lead singer and rythme guitarist for Tenacious D, and then managed to become an actor from his music career. The music that he does make is hilarious, and at the same time manages to give an excellent rocking feel. He's a terrific example of showing that music can be about whatever you want it to be.