as a disclaimer of sorts, I must admit that I'm more of a reeds/bass/percussion type person, favoring/seeking out those instruments and their players in the jazz recordings that I buy/listen to, with the piano, for whatever reason, not being as high on my musical, so to speak, list. that said, in purely alphabetical order:
1. Alice Coltrane (musical sacrilege, I know, but I'll take her any day over Tyner).
2. Bill Evans (preferably with the final trio of Johnson and La Barbera).
3. Keith Jarrett (preferably from the 70s and preferably with the "American Quartet").
4. Herbie Nichols (the jazz great whose complete discography is the easiest to own and, indeed, SHOULD be owned).
5. Mal Waldron (don't own too many titles featuring him, but I enjoy his playing on all of them, to be sure).
oh ... and I guess that I should note, before I submit this, that my most favorite of pianists are a bunch of folks not primarily known for that instrument. that said, they are: Don Cherry, Charles Mingus, and Sam Rivers. given that you asked for pianists, I wasn't sure if I should include them above. I know that I couldn't leave them out, though...