Without a doubt, my first selection would have to be James Taylor.
Followed closely by Santana; Led Zeppelin; The Who; The Rolling Stones; The Byrds; Buffalo Springfield; Neil Young; Crosby, Stills and Nash (and Young); Jackson Browne; Bob Dylan; Joni Mitchell; Emmy Lou Harris; Linda Ronstadt; The Eagles; George Harrison; John Lennon; The Jefferson Airplane(but not the Starship); Hot Tuna; Jethro Tull; The Doors; Jimi Hendrix; Johnny Winter; Steppenwolf; Eric Clapton; Cream; Early ZZ Top; Warren Zevon; The Allman Brothers; Warren Haynes and Government Mule; Lynard Skynard; Bad Company; Pure Prairie League, Jerry Garcia; The Grateful Dead; Little Feat (old and new); Lowell George; Steely Dan; Donald Fagen; Dan Fogelberg; Spooky Tooth; AC/DC; Metallica; Tool; Jerry Cantrell;
Keb Mo; Dave Matthews; Natalie Merchant;
Weather Report; Spyro Gyra; Chick Corea and Return to Forever; The Yellowjackets; Fourplay; The Rippingtons and Russ Freeman and Craig Chaquico; Steve Morse; Stevie Ray Vaughn; Buddy Guy; Albert Collins;
Nightnoise and anything off the Wyndham Hill recording label;
These are just a few artists out of my thousands of lps and cds that have had a lasting effect, and are generally in heavy rotation.
