During the exchange of gunfire at the end of the movie, the man returning fire on the one who shot Willie Stark fires at least ten bullets from a six-shot revolver.
In the locker room scene, the towel draped over Tom's shoulders keeps changing positions.
Near the end of the movie, on the courthouse steps, Stark is shown from the front with Sugar Boy standing directly at his right shoulder. From behind, however, Sugar Boy is nowhere near Stark.
When Tommy first takes the field, the referee is towards the left and Tommy is to the right, really not anywhere near each other, yet the ref's arm is visible in the close up.
When the doctor is playing a waltz at the piano, the right-hand portion of the music continues even when he lifts his right hand -- twice! -- to pick up a drink.
Shortly after the beginning of the movie, after Stark and Burden leave the pool hall, the car is driving on the dirt road and passes the camera position. The camera's shadow can be briefly seen on the side of the car.
Sometime Jack's girlfriend's name is spelled Ann (as in the first newspaper article on her) and sometimes it's spelled Anne (as in a later newspaper article on her).