This dude named Neil Pearlman's pretty good at piano. I don't know enough about jazz or classical to have a favorite pianist in those genres, but Neil is someone that I model a lot of my folk playing off of, though he's a lot better. He isn't perfect, but he isn't ashamed of it, as the few errors are a casualty of reckless creativity.
He is also good at filling out the spaces of rhythm and timbre in the space of any song, in a way that complements the other performers excellently.
Here's a good example of his prowess in accompaniment. Starts a little slow I guess, but the end is quite lively, and it is pleasant all through.
For guitar, I can share
this bit of greatness, but my favorite player's probably gotta be Mike Vass.
Settled in Clay is an absolute masterpiece.