Revealing mistake: When the guy jumps through the window with the chainsaw he lands on a black crash mat, which moves on landing.
Continuity mistake: When Tony shoots Manny after he finds out that he has been with Gina, she runs to hold his bloody body, in turn getting blood on her robe. A few scenes later, when Gina comes into Tony's office, wearing the same robe, it is perfectly clean and there is no sign of any blood. (02:27:50 - 02:30:00)
Continuity mistake: When Tony is in the Babylon Club watching the performer dressed in a clown suit, the assassins shoot everyone, including the clown. When the clown is first shot, his hat falls to the ground (but the camera cuts away). After a few seconds later, we see the clown again falling, but his hat is back on top of his head.
Continuity mistake: Tony tells Nick to call Lopez at exactly 3:00. The scene goes on with Lopez and Bernstein dying when they ask Ernie if he wants a job. The clock says 3:03 but, from the time the call was made at 3am to the next time we see the clock next to Ernie, 5 min and 25 sec have passed. (01:33:00 - 01:40:00)
Other mistake: In the scene that begins with "Three Months Later" where Tony and Manny are sitting at the table near the beach watching the girls in bikinis walk by, Manny is attempting to explain to Tony how to pick up women by explaining what "women in this country know and understand". After Manny sticks his tongue out to demonstrate and Tony asks Manny "what the f*ck was that, Mayne?", if you watch Al Pacino's lips as Steven Bauer is talking, you can see Al's lips moving in unison to whatever Steven is saying.
Continuity mistake: In the final scene where Tony is killed, he is shot, then falls through a banister. When he first falls through the banister both halves are pushed outwards. The next shot is from below looking upwards and shows one half of the banister coming outwards and the other going inwards. Then it goes back to the shot from above and both halves are back outwards. (02:36:30)
Continuity mistake: In the scene at the beach/pool where Manny approaches the blonde in the blue bikini, if you watch the area of the pool behind where the blonde is seated on a lounge chair, you will see several people in the pool. Immediately after Manny sticks his tongue out at her and the camera pans back to her as she slaps him, if you look at the same area of the pool, there is absolutely no one there anymore. This was only a matter of seconds after seeing everyone there.
Visible crew/equipment: In the scene where Tony goes back to his mother's house to visit her and Gina, watch the bottom right corner of the screen, on one of the kitchen appliances. You will see a shadow moving through the area, but no-one in the scene is moving at this speed or direction.
Visible crew/equipment: When the camera pans down, at the scene of the Carlyle sign, the crew members can be seen moving the camera crane in the reflection of the last window.
Revealing mistake: When the man is pushed out of the helicopter and hung by a noose around his neck, in the brief close-up shot you can see the prop noose around his neck is very loose and partially conceals the real rope that suspends the victim.
Revealing mistake: As soon as Tony shoots Hector out on the street, the shot changes angles to see Hector's body fall face down. It may be a stunt-double because this person's hair is completely different from the actor playing Hector. Before Hector is shot, his hair is completely combed. As his body is falling, his hair is suddenly completely uncombed (To me it seems the double's head is bald on top and with a tiny pony-tail, but that's probably just me). After he falls his hair seems back to being combed-over.