When "the neighbors" are torturing some unknown criminals - the leader is standing on one guy, hitting golf balls at another guy who is hanging upside down in his underwear. The first golf swing is using a metal wood, then he asks for a five iron. However, the club handed to him is clearly not a five iron, but another metal wood.
In the director's cut, when Kenny and Gary have stolen the guns and the old man shoots a hole in Gary's hair, Dean says, "are you all right, Gary?" His lips ask "Gary?" again, but is only heard in the next shot of the smoking hair. The original region 1 version has the sound in sync with the lip movement.
When Dog describes Golf as a "way to spoil a good walk" he attributes the quote to Winston Churchill. The quote "to play golf is to spoil an otherwise enjoyable walk" first appeared in 1903 in a book by H. S. Scrivener.
During the closing sequences of the film where Tom is seen wearing a woolen hat, his long hair is visible at the back in many shots. This is despite his character having short cropped hair throughout the rest of the film. (see trivia)
When Tom is explaining the cheque scam to Soap and Bacon, in the last shot of Soap and Bacon the liquid level has lowered in the glass in front of Bacon but Bacon is not drinking from it. In the same shot there is also an extra cigarette butt in the ashtray although Soap doesn't stub out his cigarette.
Just before Plank gets shot in the neck with the air rifle, he is looking to his right with the left side of his neck exposed. But when he is shot, the close-up shows him holding the right side of his neck.
When Winston opens the security gate, he leaves the keys in the gate, then after Dog butts him and drags him to the stairs, Winston still has the keys in his hand. When he gets to the top of the stairs, the keys are no longer in his hand.
When Rory Breaker's henchmen visit the dope house in the evening or at night (it's dark), they find J who has come around and screaming in pain. Which means that the police still hasn't come to the house. This is highly improbable, since there was a shooting there during the day. Dog's men had fired shots with the very loud Bren gun in two separate occasions, and Gloria also fired it after them, emptying out the magazine. Even if there was nobody else in the building, the shots would've been heard from at least a couple of blocks away, and the police would have come.
As Tanya, the dealer, is explaining the game of Three Card Brag she completes the initial deal. She accidentally exposes the bottom of the deck which would be visible by all players as a 7 of diamonds. This should have resulted in a misdeal.
The goof items below may give away important plot points.
It was said that Eddie had a gift of reading the slightest reaction in an opponent in a game of poker, yet, when Harry makes a very noticeable reaction with his eyes, Eddie continues to bet a huge sum in the face of imminent loss.
When Hatchet Harry and Barry the Baptist are killed, neon lights can be seen against the dark background through the window behind Harry, but they would only be visible at night, though the event occurs in daytime as seen in the next shot outside the building when Eddie and Tom enter.
Before Dean is shot by Hatchet Harry, there is clearly visible a prop between Dean's body and shirt for blood splatter. Even after Dean's been shot and is lying outside Hatchet Harry's office, the prop is also visible under the shirt.