Revealing mistake: In the scene where Tom Cruise is yelling at/questioning Dawson at the jail in the witness room, immediately after Cruise gets up in Dawson's face and says, "I'm the only friend you've got," Cruise is supposed to simply turn and walk away. But you can see from the angle behind Dawson that Cruise' first step is a step down, indicating that he was on a pedestal of some sort to bring their heights closer together.
Revealing mistake: In one scene, Tom Cruise is walking along the sidewalk with Kevin Pollak (who is pushing a pram). The camera, which obviously is moving backwards on a dolly, is in front of them. As the men walk past some bushes, watch the branch on the right-hand side. As it comes into view, we see it spring back and shake for a bit. Evidently, the camera dolly snagged it on the way past.