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: During the scene in the office of Bada Bing, Pauli, Christopher, Tony, Silvio and Pussy are all together and the TV is on. Pussy is reading something and Christopher is lifting weights. In between shots, the weights change from Chris's right arm to his left and back again. It could be argued that he changes arms when the camera is off him, but there is one instance where it definitely happens too quickly for this to be the case.
Plot hole: In the scene where the FBI plays the tape to Tony and reveals the conspiracy between his mother and Junior, it is stated that the bugs were placed at Green Grove. However, the second conversation played in the sequence actually took place outside a movie theater the episode prior, which would not have been recorded as part of the Green Grove surveillance. The conversation involves Livia telling Junior that Tony reminded her of her cousin Kiki after she had her lobotomy.