Well, my rotation changes constantly, but here's a random list of artists I like from each genre:
ROCK/CLASSIC ROCK--The Beatles (and their solo stuff), The Rolling Stones, Cream (and Eric Clapton solo), The Doors, The Allman Brothers Band, Little Feat, Bruce Springsteen, John Mellencamp (his '80s' stuff), The Turtles, Frank Zappa
HEAVY METAL--Kiss, Motley Crue, AC/DC, Black Sabbath, old school Ozzy Osbourne (1980s'), Van Halen (before David Lee Roth left), Led Zeppelin, Grank Funk Railroad, old Metalica
FUNK--Parliament/Funkadelic, Bootsy Collins, The Ohio Players, James Brown (late '60s'/early '70s'), Kool & The Gang (before '78), Cameo, Lakeside, The Isley Brothers, some Curtis Mayfield and Issac Hayes, The Brothers Johnson
SOUL/R&B--Barry White, The Delfonics, Marvin Gaye, Stevie Wonder, Al Green, Johnnie Taylor, Joe Tex, Sam & Dave
BLUES--Albert Collins, Son Seals, Koko Taylor, Muddy Waters, Slim Harpo, Lonnie Brooks, Katie Webster, Little Walter, Mississippi Fred McDowell, Blind Willie McTell, Big Bill Broonzy
JAZZ--Miles Davis, Herbie Hancock, John Coltrane, Chick Corea, Shelly Manne, Gerry Mulligan, Dave Brubeck, Louis Armstrong (especially his HOT FIVES stuff from the 1920s'), Vince Guaraldi
REGGAE--Culture, Eek-A-Mouse, Augustus Pablo, Bob Marley & The Wailers, Judy Mowatt, Marcia Griffiths, Derrick Harriot, Alton & Hortense Ellis, Yellowman, some Lee "Scratch" Perry
PEACE!