Garteful Dead is my #1 favorite. I'm a longtime Deadhead and went to about 40 shows between '86 and '95. As the saying goes "There Is Nothing Like A Grateful Dead Concert"

Other than that I mostly listen to classic rock but also listen to some reggae, some metal, and some jazz
Beatles
Doors
Floyd
Hendrix
Allman Brothers
Gov't Mule
Steely Dan (yes, Steely Dan does fit into "classic rock")
Phish
Bob Marley