You are all looking way too late. Nat King Cole? Duke Ellington? Jelly Roll Morton? Benny Goodman? Artie Shaw? Count Basie? Miles Davis? Come on. Not all music is rock. Without jazz, rock wouldn't even exist.
Although I would like to commend Elvis Presley, Buddy Holly, Chuck Berry, The Beatles, Led Zeppelin, Bob Dylan, Jimi Hendrix, The Rolling Stones, Frank Zappa, Queen, The Who, Bob Seger, Aerosmith, Iron Maiden, Ozzy Osbourne, AC/DC, Fleetwood Mac, Lynyrd Skynyrd, Alice Cooper, Pink Floyd, Judas Priest, Sex Pistols, Nirvana, U2, Bruce Springsteen, Metallica, Pearl Jam, Ramones, Blink-182, and Guns N Roses for their contributions to rock and metal.
Then there's the Pop/Motown classics: Stevie Wonder, Michael Jackson, The Temptations, The Four Tops, The Supremes, etc.
And although this will destroy any credibility my judgment has, some hip-hop groups have to be mentioned. NWA, Wu Tang Clan, Outkast, Public Enemy, A Tribe Called Quest, even the Gorillaz.
Of course now for daring suggest that anyone other than a guitarist has contributed to modern music, I'm liable to be mobbed.