Audio problem: When Parker and Sid are fighting on the rooftop at the end, watch and listen because when Parker jumps to the rail where Sid is. After managing to barely climb over the rail, he punches Sid. About two seconds later, the punch sound takes affect after the scene is gone.
Visible crew/equipment: Toward the end of the film, when Parker and Sid 6.7 are back in the computer simulation, Sid lifts Parker over his head and throws him off the roof. When he does this, you can see a hook and a rope lifting Parker over Sid's head. His shirt is even pulled by the hook.
Continuity mistake: In the wrestling arena scene, Russell Crowe has his hand blown off by a shotgun blast. He makes his way into the ring, then shortly afterwards jumps out, using both hands to steady himself on the wall. When he comes out of the stairwell to the train platform his hand is missing again.
Other mistake: Whilst Barnes is trying to disable the bomb, he uses one of the wires from his arm to try and loop the video and timer on the bomb. After he connects the wire the timer countdown changes from 0:03 to 0:43 and the loop of Sid saying "I already thought of that, faster." Barnes immediately comments its not working, before seeing it countdown again to 0:03 and resetting to 0:43, now commenting it's working. The fact that the timer reset the first time, it seems strange he wouldn't comment the timer didn't work the first time. There is a strong likelihood this was done to cover up not having a shot to insert of the timer continuing to count down.
Other mistake: At the club, Sid likes the blue suit and takes it. But he is still wearing the suit he came in when Denzel's character shows up and is not carrying the blue suit as he leaves. If he somehow had it concealed on him it would have been shot up when he was thoroughly shoot. Yet when we next see Sid he is wearing the blue suit and there is not a mark on it.