The Wikipedia article
Bagram torture and prisoner abuse documents two homicides by U.S. military torture.
Damien Corsetti gave
an interview in which he claimed regular physical abuse that was not accompanied even by interrogation.
A couple of years ago I heard an interview of
Benamar Benatta, who claimed that he was regularly beaten and kicked for five years in U.S. prisons in order to extract terrorist information from him, even though he had been cleared by the FBI and INF of any connection to 9/11 within only a few months of his illegal extradition from Canada.
This U.S. Department of Justice training report against abuse mentions that "the Benatta case is one of many examples in which particular arms of the criminal justice system—-law enforcement, prosecution, INS agents—-target individuals based on inadequate or incomplete information on the assumption that further incriminating information (that is, giving up names of associates) can be squeezed out of them while they are in custody." The references to "overreactive responses" and trying to "sqeeze out" information appear to be incidental or intentional confirmation of Benatta's story of physical abuse.
These incidents happened in part because the Bush Administration in its early years argued for this definition of torture in the "standards of conduct for interrogation":
"equivalent in intensity to the pain accompanying serious physical injury, such as organ failure, impairment of bodily function, or even death." Parse that definition carefully and you find that any practice up to but not including death may fall outside the legal definition of torture.
As for waterboarding, the article
Waterboarding: Still Torture After All These Years notes that waterboarding was regularly practised by the Khmer Rouge and the Nazis, and that the United States tried and convicted Japanese soldiers of inflicting it on U.S. soldiers as a war crime.