Little Walter (born Marion Walter Jacobs in Marksville, LA, and raised in Alexandria, LA) (May 1, 1930 - February 15, 1968) was a blues singer, harmonica player, and guitarist. (source for this paragraph is Wikipedia)

Tired of the generic electric guitar blues of his time (1945), Little Walter introduced to blues a new sound by simply combining the use of a guitar amp, mic, and a harmonica; a technique used among harmonica musicians to this day. Little Walter thus became the first musician to use electric distortion on purpose.
Little Walter is widely regarded as the best harmonica player ever, and you can hear much of his talent accompanying Muddy Waters's repertoire from the 50's, as well as his own numerous and successful recordings of that time.

Jacobs is generally included among blues music greats: his revolutionary harmonica technique has earned comparisons to Charlie Parker and Jimi Hendrix in its impact: There were great musicians before and after, but Jacobs' virtuosity and musical innovations reached heights of expression never previously imagined, and fundamentally altered many listeners' expectations of what was possible on blues harmonica. His body of work earned Little Walter a spot in The Rock and Roll Hall of Fame in the sideman category on March 10, 2008, making him the only artist so honored specifically for his work as a harmonica player.(source for this paragraph is Wikipedia)