Continuity mistake: When Samuel Jackson is about to be shot by the two corrupt cops, the Vanessa Williams character comes up from behind and shoots the black one in the head and he falls down. Then, they show her talking, and the same black man's arm and partial shoulder are in the shot.
Factual error: In the scene where Shaft has chased the guy running from the drug bust and caught him in the hall with an empty gun you can plainly see the slide is locked back on the bad guy's pistol (indicating an empty magazine). When Shaft steps out to arrest him (before the bad guy jumps out of the window into the other building) you can clearly hear the 2 clicks of a firearm hammer falling on an empty chamber. With the slide locked back, the hammer is locked back also...it would never make any clicks.
Continuity mistake: When Shaft and Peoples have the final duel at the end of the movie, you'll notice Shaft has a holster across his right arm and there is a gun in it. When he grabs for the gun, he reaches into the holster, but when they get the close up of him pulling the gun out, you can clearly see he is reaching under his shirt, and the holster's disappeared.
Visible crew/equipment: During a car chase with People's gang, Shaft blasts away at the baddies causing their car to crash and somersault over other parked cars. Just along from this carnage, there is a huge studio spotlight just in an ally along with other lighting equipment illuminating the scene.
Audio problem: While rescuing the witness from her safe house near the end of the film, Shaft and the witness run across the street to Shaft's waiting car. They comes under a barrage of gun fire from the driver of People's car. The shot shows his gun breech is empty and the actor is just pulling the trigger while the effects sound like he is firing.