After the officers gear up for the final battle, in nearly every shot of them approaching the supermarket, the sound of guns being cocked is heard, even though no one is actually cocking a weapon. Further, there's more cocking than there are guns in the scene.
Sgt. Angel is meant to be the best of the best so far as Police Officers go yet he is often seen with his handcuffs the wrong way round. If he removed his handcuffs as he has them he wouldn't be able to apply them as the fixed double bar would be facing the suspect's wrist as opposed to the movable single bar.
During the introduction whilst Sergeant Angel's life in the police is summarised, he says that he was stabbed by "a man dressed as Father Christmas," and when he knocks on the door, you see a scar on his right hand, with which he is knocking, but the flashback of him being stabbed shows "Father Christmas" stabbing him in the left hand.
When Sgt. Angel first approaches his room at the Swan hotel, the camera lingers momentarily on the room door's prominent sign which reads "CASTLE SUITE". Angel hangs up his jacket on a hook, but seconds later he decides to leave. Angel removes his jacket from the hook and opens the door to leave - and the "CASTLE SUITE" sign is gone.
When PC Doris Thatcher comes in bringing PC Danny Butterman his birthday cake she is wearing fake boobs over her sweater, seconds later the fake boobs are gone even though she is holding the cake with both hands.
When the officers are pushing the shopping carts to ram the meat counter, it shows Doris and Sgt. Fisher standing off to the side providing covering fire and when the officers pushing the carts go by they fall in behind. In some subsequent shots Doris and Fisher aren't there and in another they are just falling in behind when they should have already been there.
When Danny and Nicholas are trying to put the pieces together, just before Frank enters the room, Danny says "Maybe they were all accidents." In response to this, Nicholas puts his arms on the desk and rests his head on them. When Nicholas gives a small laugh a few moments later, it changes to a close up of him and his arms are at his sides with his head directly on the desk. The change of shot was very quick, with no time for Nicholas to move his arms.
When Danny takes Nicholas away from the village and gives him his car, Nicholas is seen in the boot (trunk) of the car. After he gets out, neither he nor Danny close the boot, but it is closed when Nicholas drives away.
After Frank gets away from Danny at the model village near the end of the film and takes Danny's Police car, he drives the car through a fence into a very large, empty field. After the swan attacks Frank in the police car, it shows Danny and Nick watching from the model village as Frank's car careens into a tree in a much smaller field. For some reason they filmed this sequence in two separate locations.
When Nicholas and Danny stop Martin and Eve for speeding, Eve is playing with her hair when Martin says, "I'm playing the eponymous hero." In the next shot, from the front, both her arms are by her sides nowhere near her hair.
When the kids spray-paint the lenses of the CCTV cameras, the CCTV monitors show the colour of the paint that was sprayed on. In fact, the monitors would show only the colour black because no light would be reflecting back from the painted surfaces.
When Nick and Danny confiscate the vast arsenal of unlicensed weapons from the farmer they don't arrest him despite the fact that possession of guns such as pistols in the UK would be highly illegal and earn the man many years in prison.
When Angel goes to a crime scene to talk to his girlfriend Cate Blanchett, who is a Crime Scene Investigator (CSI), the room is packed with CSIs, at least 8 of them. In real life there would not be this many in a small room like this and, as Nick Frost points out during the DVD commentary, it could even spoil the physical evidence they're trying to collect.
In the scene inside the church just after Tim Messenger is murdered, Frank Butterman tells Doris Thatcher to "get the CSI down here". 'CSI', standing for 'Crime Scene Investigators' is an American term, the British equivalent being 'Scene(s) Of Crime Officers' or 'SOCO'. However, this may have been deliberate, as, due to the TV series, the British public are likely more familiar with the term 'CSI'.
When Nick arrests Danny for drink driving he simply throws him in a cell and leaves him to be dealt with in the morning when he has sobered up. In reality he would have had to book him in with the custody Sergeant, establishing his identity and taking mugshots, fingerprints etc before making him take a drink drive breath test to see if he was over the limit.
When the mine detonates at the end of the film, the prong sinks into the mine. The prongs of a naval mine are made of a soft metal (usually lead), designed to bend, not sink in, on contact with a ship's side.
When gearing up in a final scene they show pump shotguns being cocked and a double barrel 12 gauge being closed with two shells loaded. Both shotgun shells in the double barrel shotgun clearly show the primers being already fired, probably being used for safety.
The goof items below may give away important plot points.
The seats in Simon Skinner's light blue Jaguar XK convertible alternate between a pre-2000 model year and a post-2000 model year car - the difference being adjustable headrests. The headrests are adjustable when Skinner is present at the Blower-Draper "crash", but the seats are one-piece seats when Skinner drives past Angel after Merchant's death.
The position of the torch (flashlight) Sergeant Angel is holding after he briefly holds Danny hostage changes, from his left hand as we see the back view of him running through the arch to his right hand as we see the front view.
In the car chase at the end of the movie, Frank Butterman takes out the driver's side door to Danny's police car. In the following cuts, the exterior shots show the door missing, but the interior shots show the door still intact.
In the final scene where Frank's gun is pointed at Nicholas, Danny grabs it, but when changed to another angle, he grabs it again. This is similar to the scene where Nicholas is in the prison cell and turns around to look at Danny, but from another angle, he turns his head a second time.
After PC Danny Butterman is shot by Tom Weaver and lands on the floor, Mr Weaver falls into the evidence room and sets off the mine. The Police station then gets blown up. But when Sgt. Angel finds Danny after the explosion rather than Danny being covered with debris he is lying on a pile of debris and not on the floor where he started.