In the scene where Marcus says "Crack meant money, money meant power, power meant war," a blue 1965 4 door Impala drives up to 3 guys standing on the side walk. when the scene switches to showing those guys being shot the car changes to a Blue 1964 4 door Impala.
When Keryl, Marcus and Justice go to take revenge and hit the Colombians back, Marcus gets out of the car immediately after it stops, but in the next shot he is still inside chatting with his buddies about the weapon.
When Marcus gets his Mercedes Benz S500, he starts playing
his Window Shopper song. He wasn't a rapper back then. This is not an actual goof, as the tape Marcus was listening to was his demo tape, and he was in the car to drive to a meeting with a producer that was going to listen to his demo.
When Majestic is discussing killing the police to Marcus, the shot of the Uptown station house has the same figure ascending its steps in both shots, revealing that one shot was used twice instead of actually using two separate shots of the same location.
The goof item below may give away important plot points.
Toward the end of the movie when the kid walks into the street then turns to shoot the cop through the LF window of the car he does so killing the cop. In the very next scene with him running from the scene, the car is in the background with the LF window rolled up.