I second the vote for Joe Benevenia.
Other great, "big dog" tumor surgeons:
Sybil Biermann, MD (University of Michigan)
John Healey, MD (HSS/Memorial Sloan-Kettering/Cornell)
Carol Morris, MD (HSS/Memorial Sloan-Kettering/Cornell)
Kim Templeton, MD (University of Kansas)
Kristy Weber, MD (Hopkins)
Folks, I can't believe no one mentioned Mary O'Connor, MD, the Department Chair at Mayo-Jacksonville. She developed most of the MIS THA and TKA techniques and she is also a tumor surgeon.
Foot/Ankle:
Sheldon Lin, MD (UMDNJ/NJMS)
Steve Sheskier, MD (NYU/HJD)
Naomi Shields, MD (Kansas)
Traumatologists:
Lisa Cannada, MD (Saint Louis University)
Mike McKee (Toronto/St. Michael's)
Ted Miclau III, MD (UCSF)
Bert Moed, MD (Saint Louis University)
Paul Tornetta III, MD (BU)
Joints/Adult Reconstruction:
Matthias Bostrom, MD (HSS)
Tom Einhorn, MD (Chair at BU -- monumental figure)
Bob Buly, MD (HSS)
Mary O'Connor, MD (Chair at Mayo-Jacksonville; see above)
Paul Pellici, MD (HSS)
Pediatric Orthopaedics:
Fran Farley, MD (U. of Michigan)
Chuck Mehlman, DO (U. of Cincinnati)
Susan Scherl, MD (U. of Nebraska)
Sports/Shoulder surgeons:
Jeff Abrams, MD (Princeton, NJ)
Julie Bishop, MD (Ohio State)
Struan Coleman, MD (HSS)
Jo Hannafin, MD/PhD (HSS) -- has a PhD, too: extremely impressive
Scott Rodeo, MD (HSS)
Tom Wickiewicz, MD (HSS)
These guys are all rock stars and there are many others. This is just to name a few.