SpeedOfThought

There indeed haven't been that many people who've focused on experimental guitar sounds that I've come across and I've listened to a ton of music. I really love it though and compiled a little list of 200 artists to check out at my lastfm group "experimental guitar and noise guitar".
My personal favorites are Agata (from Melt-Banana, has a solo album too), Igor Ogogo, & Omar Rodriguez-Lopez. If you really want to hear the craziest, most extreme avant-garde guitar sounds, then you won't be disappointed with God Generator's discography.