Deliberate mistake: O'Niel needs a sample of a dead man's blood to test for toxic drugs. So he visits the corpse, which has been dead for quite some time and is lying on its back, and proceeds to insert a hypodermic syringe into the dead man's frontal neck, extracting the sample. But blood pools low in the body soon after death. There ought to have been no blood available from that location of the body. To get blood, O'Niel should've punctured the corpse's underside.
Deliberate mistake: When Max opens the dog food, the lid should be all jagged because of the type of can opener he uses, but when dog and the gyro captain have the can the lid is cut smoothly. This was done so dog didn't get cut whilst eating out of the can.
Deliberate mistake: When the scanners escape the apartment in the van and the assassins are in pursuit there is a street view shot of the assassins driving up next to the scanners' van. If you watch the street on the right side of the screen you can see people stood watching the filming in groups, out of harms way. (00:50:28)