Has anybody ever been revived from brain death?

No; not that I have ever heard of or been able to find in any of the medical literature databases. Brain death is pretty much the definitive diagnosis of permanent death, and revival attempts after the cessation of brain activity are pointless, brain activity does not re-start after it has ceased being detectable. What is very difficult for relatives and friends of those who have gone into brain death to take, however, is the fact that the heartbeat is not controlled by the brain -- it arises from within the muscle of the heart itself -- so as long as the brain-dead individual is on a breathing machine the heartbeat will continue steadily, skin tone will continue to be good, and the individual will give the appearance of someone who is just in a coma.

The closest to revival after brain death that anyone has come is through a phenomenon known as "cold-water drowning". This is a mammalian reflex which kicks in if someone is submerged in very cold -- and I do mean VERY cold, as in one or two degrees above freezing -- water; blood pools around the heart and in the brain, and the body shuts down rapidly. People have been successfully and fully revived from cold-water drowning after more than an hour without a heartbeat or oxygen. However, even in this state there is barely-detectable brain activity.

The most miraculous revival in recorded history, I personally think, was Dan O'Reilly of Edmonton, Canada. In December 2004, at the age of 54, he was actually drowned while vacationing in Mexico, a warm-water drowning. He was pulled out of the water after an estimated 45 minutes of oxygen deprivation, and flown to a Houston medical center on life support. In Houston Dr. Joseph Varon, a critical care specialist, froze him, inducing the cold-water drowning phenomenon even that long after the fact, after which he was able to put O'Reilly into a "normal" coma. O'Reilly woke from the coma around March 5, 2005, and after about six months of intense therapy was able to walk out of hospital under his own power and return to his family; he is even able to talk about the experience. However, the freezing actually acted to protect and preserve brain function; although he was on the edge of brain death, he never quite slipped over that line.