Attendings from both the PI and ACFAS schools of thought are big contributors to our profession. For that reason I second Feli's opinions and would also include Doctors Chang, Grossman, Mendicino to the mix, amongst other faculty members (ACFAS and PI). Although my experience in the field is still relatively young but I have been fortunate in rotating with Dr. Dane Wukich, MD who is a big supporter of our profession, and in my mind a great educator as well.
The ultimate attribute that these attendings/directors share is the passion and drive to continuously improve themselves and those around them. I'm sure that there are many more contributors to our profession but from my experience thus far, the aforementioned surgeons have been very influential.