Continuity mistake: When Denzel Washington is injected with the tracking device,it is injected behind his ear. But later, when he looks at his cop friend and says something to the effect of "Get my gun", the band-aid is on the side of his neck.
Continuity mistake: Right after Sid comes to life he cuts his finger off. When you see the actual cut, it is just the tip of the finger, but when you see his hand afterwards, it is more than half the finger that is missing.
Continuity mistake: When Parker is chasing Sid through the studio building, there's a scene where ricochets are sparking all around Sid even though the previous shot shows Parker pinned down by Sid's gunfire.