Factual error: During Tony's assassination attempt he struggles with one of the "hit men" for control of a pistol. One can see that the pistol does not contain a magazine.This would limit the shooter to 1 shot, providing the pistol is not equipped with a "magazine disconnect" if it is than it can not be fired at all. It seems unlikely that a "hit man" would be so ill prepared.
Continuity mistake: When Paulie Walnuts is talking to Tony in the hospital room, the close up of the heart monitor shows the heart rate in highlighted text, with the word "Tachycardia" flashing. In the shot from Paulie's point of view, the heart rate is in normal text and "Tachycardia" is not flashing.
Continuity mistake: In the scene where Bacala is telling Uncle Jun about his father and the accident, Uncle Junior gets angry and starts throwing things around, he is wearing glasses. You can see that in between throwing one of the items, he is not wearing his glasses, then he is wearing them again.
Revealing mistake: While Christopher and Furia are dismembering Richie Aprile on a meat saw, you can see that the blade of the saw is still, but the blood is splattering all over the place and you can hear the sound of the meat saw cutting through flesh.