Continuity mistake: On the final mission, once you kill the final boss, the gun you will be holding in the cut scene is a M4, even if you used a different gun.
Factual error: During his interview on K-Chat, B.J. Smith says "Like the song says, 'don't call it a comeback.'" The song he's quoting is "Mama Said Knock You Out" by L.L. Cool J, which wasn't released until four years after the game takes place.
Other mistake: In 'Keep your Friends Close,' in the first cutscene, Tommy says put 20 million in cases, but the subtitles say three.