Final answer:
Tony Iommi, the founding lead guitarist of Black Sabbath, cut off the tips of two fingers which led to the creation of a unique sound for the band.
Step-by-step explanation:
The founding lead guitarist who accidentally cut off the tips of two of his fretting fingers in a sheet metal shop when he was 17 is Tony Iommi of the band Black Sabbath.
This incident occurred before Iommi achieved fame with the band. Despite the injury, Iommi created homemade prosthetics from melted plastic bottles, which he attached to the stumps of his fingers, and tuned his guitar down to ease the tension on his injured fingers, leading to a darker, heavier sound that became a signature of Black Sabbath's music.