Deliberate mistake: Near the end, after the case is dismissed, people are celebrating, and we see a reporter talking, with snow flying around him. Cut to another shot of people watching a television. The snow has disappeared from the reporter's shot. It's likely that, since the snow was added in post, the filmmakers forgot to include it in that one shot.
Deliberate mistake: While Jimmy and Billy are being chased by the jet skis one of the baddies fires a missile, and when it lands in the water the long shot is flipped, note "AKZO" is backwards. (00:49:25)
Deliberate mistake: During the final battle, at one point Sean kicks Crane off a rope bridge. When this happens, if you look closely you can see the rope railing on the side of the bridge fall away right before Crane falls. It's supposed to look like Crane is falling through the ropes, but they drop just a split-second too early (he's not even touching them when they start to fall), so it was done on purpose and mistimed. (It was likely timed to drop away just a split-second before Crane fell so that the stunt-person wouldn't accidentally get tangled in the ropes as they fell).