Continuity mistake: At the end of the fight on the beach, the Seminole is too far away to have hit Shale.
Revealing mistake: Look at the gun fired behind Shale at the firing range. The person doesn't pull the trigger, there is no flash, the slide doesn't move, there is no smoke. But the gun still kicks.
Plot hole: When Tom Berenger is talking about Vietnam, the school bell rings and everyone leaves class. After everyone leaves, Tom Berenger puts the ice pick in his overcoat and quickly picks up his briefcase and opens it. Around 10 to 20 seconds after the bell rang, he looks at the portable surveillance in the briefcase. He flips through all the cameras. How did the entire school clear out with no one in site from the time the bell rang? Are there not usually some people around in the hallways after school?