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.
Continuity mistake: Watch Shaft's goatee. The strip of hair running vertically under his lip constantly changes in thickness throughout the movie. At one point it will be wide and in the next scene it will be noticeably thinner only to change back to wide in the following scene.