As Billy is about to leave the apartment after the "drink of water" fight, Gloria's shirt is pulled to the side and her right breast is fully exposed. In the next shot of her she hasn't moved but the shirt is in a totally different position.
While Billy confronts Sidney about being hustled out of $1700, he stuffs his hat into his jacket pocket. In the very next shot, when Sidney is responding to his accusation, Billy is putting his hat into his pocket again.
When Gloria is on Jeopardy!, the man to the left of her has $100, but after she answers the daily double he has $2800. he did not have a chance to ring in since she answered all the questions up until the daily double.
During the final game of the tournament where Woody Harrelson and Wesley Snipes play "Willie" and "Flight," Harrelson takes a jumper from the top of the key and the rebound appears to come back to him, but in the next shot, the ball resides with "Flight."
When Billy and Sidney are driving back from their first basketball hustle, Sidney is in the middle of the backseat for all of his lines. When Billy is talking, however, Sidney's left arm is clearly visible on the left-hand side of the car.
Just before Gloria packs up her clothes and leaves the motel room, she takes off her red shirt and tosses it on the chair next to the front door. When she's packing her suitcase, the shirt is on the bed.
At the end of the first hustle game, Wesley Snipes dunks, bounces the ball off his leg, and the ball is caught by Harrelson. In the next camera shot, when Snipes lands on the ground, the guy behind him catches the ball coming down from the hoop.
When Gloria is on Jeopardy she answers the first question wrong and is in the negative. She answers another question worth a hundred and that brings her to "0" then she answers another 100 dollar question but her score already shows she has 1500.
When Woody is talking smack to Willie at the tournament about building a house with all of his bricks, Willie makes a comment about Aunt Mae's Beanpies. When they cut to the next scene with Woody and Wesley, Willie is in the background yelling the exact same lines he was just on camera saying.
After Sidney invites Billy to play against Eddie 'The King' Faroo and Duck Johnson. Billy tells Gloria that he can guarantee victory and puts his arm around Sidney's shoulder. In the next shot, Sydney's hand is on Billy's shoulder even though he hasn't had time to move.
At the end of the scene where the Stucci brothers photograph Billy, one of the brothers gets into their van, the other walks in front of camera behind the van and as soon as he leaves the shot the van drives off leaving him no time to get in.
Before the second hustle game in Watts, Sidney declares the game to be "make it take it", meaning a team retains possession of the ball after scoring a basket. However, after Billy makes the first shot of the game, their opponents (Robert and Zeke) take possession of the ball.
When Billy got home after the 2-on-2 tournament, right before he told Gloria he lost his half of the prize money, Gloria lights the candles on the table and walks over to the light switch and turns the lights off. When she walked over to the light switch it was in the down/off position and you can plainly see that she only touched the switch, she didn't flip it up or down so the lights couldn't have been turned off by her.
Sydney's definition of "hearing" Jimi Hendrix, is not the standard textbook definition of "hearing," The definition of "hearing" he is referring is African American male slang terminology that is used in southern California.
After Billy gives Gloria the dress, she lights the candles then stands up and goes to turn off the light switch. The light switch is already in the off position. But after touching it, the lights cut out anyways.
The goof item below may give away important plot points.
Incorrectly regarded as goofs
The Stucci brothers carry photos seeming to incriminate themselves. But as revealed near the end of the film, they aren't actually killing their debtors, just taking pictures making it look like they did so that they can threaten future deadbeats. If the pictures are living people pretending to be dead, these pictures are clues that the Stucci brothers are involved in further criminal activities, including loan sharking, game fixing both of which are Billy and Gloria are apart of.