Neil Young is one of my favourite guitarists. He's one of the few rock guitarists who comes close to someone like Coltrane in his willingness to explore during solos (not in technique of course, but whatever)
I used to listen to RW as a child on my parents' hi fidelity turtable in the 70s, usually on rainy days when we couldn't go outside so we'd build spaceships out of lego, play monopoly. His voice is unique. Like a sweet fortified wine.
Roger Whittaker has an amazing voice. And the whistling - I don't know how he whistles the way he does. I'm an experienced whistler myself - I do it every day, but still can't approach Whittaker's level.