Revealing mistake: While the gemstone smuggler is riding in the back seat of NY's Finest Taxi Service, in his close-ups note the vehicle's chrome button door lock, the garment hook over the window, etc. When the police cruiser makes a short stop, now in the smuggler's close-ups the door lock's chrome button cover is gone so only the inner pin remains, the garment hook has been removed, etc. (00:32:40)
Revealing mistake: When the police car is set on fire you see from the top that the flames start at three different spots, hood, roof, and trunk. Then, when the three vans drive off there's a shot from inside the police car where you don't see any fire. (00:32:45)
Revealing mistake: Towards the end of the movie, Hockney (Kevin Pollak) looks into a van and discovers it's full of cash. He is then shot from behind, and blood splatters all over the money. When his chest explodes, you can see the plastic of the bag the blood was in. (01:18:10)
Revealing mistake: During the gemstone smuggler robbery, when Verbal kicks open the van's rear doors, McManus begins to use a sledgehammer on the NY police cruiser's windshield, and behind him we see two very tall palm trees―in NYC. This scene was filmed in Los Angeles. Note the police cruiser has number 2485 at the airport and turning corners with the van tailing (filmed in NYC). As the van hits from behind it's 6423, and the stunt vehicle set on fire is 6426 (filmed in LA).
Revealing mistake: In the flashback, when the boy has his throat slit, there's no blood or wound.
Answer: Keaton doesn't believe in Keyser Soze, and is so convinced that Kobayashi is the one pulling the strings and manipulating them. They figure that if they take HIM out, they are home free.