During the end of the movie when Burt is swimming and talking to God, after he goes under water the soles of his trainers change colour as he re-surfaces.
When Sonny stops his car in front of the church, from the front camera angle, he puts his hand up to his head, but drops his hand. When the angle switches to a back view, his hand is still up to his head.
Sonny fires a single shot, and later Marlon fires six, using the same six-shot revolver without reloading.
During the landscape truck getaway Sonny and Marlon drive through a construction zone, up a trailer ramp and perform a jump. Cut scenes during the jump alternately show Marlon in the truck bed (holding onto a frame rail) and no one in the truck bed.
When Wendell Lawson slams on his brakes next to the funeral procession in front of the Church, the shadow of the Church steeple and crucifix appear on his forehead. However in the cutaway to the Church, it is clearly seen there are no shadows anywhere on the face of the Church, indicating the sun is in front of the Church and not behind it, thus unable to produce a shadow on Wendell.
In addition the size of the shadow on Wendell's face was some 3-4 inches. It could not be cast by a life size steeple, rather only by a small mock-up.