There may be a couple of other favorite pianist lists in another thread or two... Obviously Monk changed things a lot and was great. There's probably not anyone as earth shaking currently active, (maybe because now there's less new ground available to shake)... a few more good ones you might find in a jazz section:
Vijay Iyer
Don Preston
Paul Plimley
Cecil Taylor
Myra Melford
Matthew Shipp
Simon Nabatov
Achim Kaufmann
Horace Tapscott
Michiel Borstlap
Sophia Domancich
Jean Michel Pilc
Francois Bourassa
Sylvie Courvoisier
Vijay Iyer
Don Preston
Paul Plimley
Cecil Taylor
Myra Melford
Matthew Shipp
Simon Nabatov
Achim Kaufmann
Horace Tapscott
Michiel Borstlap
Sophia Domancich
Jean Michel Pilc
Francois Bourassa
Sylvie Courvoisier