During the bar fight, Joe smashes into a dividing wall, which then falls over with him on top of it. Then in the very next shot, he's on the floor several feet to the left of the dividing wall, and in the following shot, he's back on top of the dividing wall.
In the opening scene, the car that starts up to commit the drive-by shooting is a black 1974 Dodge Coronet. As it peels away from the curb, it suddenly becomes a dark green 1969 Plymouth Fury.
When Joe and Helen Layton are the lake with the two thugs, the portion of Helen's jeans right around and below her knees are already muddy before she actually kneels down into the mud, so apparently several takes had been done without having the actress change her jeans between takes.
When Joe is looking through the stack of checks in his office, the third and fourth checks that he looks at are exactly the same check.