Factual error: Max could not have been accidentally shot when Annie drops the revolver. She dropped it when she was startled by firing it into the ceiling so the hammer would still be sitting on the spent/empty shell casing. The trigger or hammer must be pulled back in order for the cylinder of a revolver to rotate to the next live chamber.
Deliberate mistake: When Michelle brings up the photo of "Fake Denzel" on her phone, she says she put it into a hidden folder. Problem? She only presses on her phone once (based on the sound you hear), and has the photo up and filling the screen within about one second. Totally preposterous. Obviously, it was done that way to keep the scene moving quickly... but there's no way a single button press and a timespan of about one second is going to bring up and maximize a photo from a hidden folder on her phone.
Continuity mistake: When Max and Brooks are having their heart-to-heart conversation on the bridge (while they are being held at gunpoint), the directions they are facing instantly changes between edits a few times. Sometimes they are facing forward... sometimes they are facing each other... etc.
Continuity mistake: During the car chase, there are a few moments where the background we see outside of the car windows doesn't quite match the background we see outside when we get wideshots of the cars driving. It usually matches, but there's 2 or 3 moments where it doesn't scatter throughout the scene.
Continuity mistake: When the two actors playing the "kidnappers " (who are part of the actual "game") break in and realise Ron the "FBI agent" was punched, pay attention. Between shots, the actors playing the "kidnappers" go from practically being shoulder-to-shoulder to suddenly being about 4 feet apart between cuts. (It happens when the one actor lifts off his mask).
Continuity mistake: When Ryan is explaining fight clubs, Annie starts to munch on a carrot. Right before the shot cuts, about half the carrot is sticking out of her mouth, and she's holding it with both hands. Instantly between cuts, she's eaten almost the entire carrot and is only holding it with one hand.
Continuity mistake: The two streaks of "blood" coming out of Gary's mouth change size and position repeatedly throughout the remainder of the scene after he is "shot" by the kidnappers. (Sometimes the streaks are thinner... sometimes thicker... sometimes close together... sometimes further apart... etc. It depends on the camera angle).