Goofs

(at around 26 mins) When Frank Castle's wife and child are in the Blazer trying to escape, it flips over. While flipping, the hand on the steering wheel is wearing a black bracelet, but when Maria crawls out of the car she is wearing no bracelets. The "black bracelets" are safety devices for the stunt driver, similar to what Sprint Car drivers wear to prevent their arms exiting the profile of the vehicle during "accidents" or stunts.

(at around 1h 45 mins) During Castle's final raid at the Saint's estate, he fires several shots into a henchman with his pistol and follows up with a "tactical" reload (replacing a semi-full magazine with a completely full one.) Castle then racks the slide to chamber a round. There would be no reason to do this as there is already a round in the chamber. If the pistol was in fact empty, the slide would've been automatically locked to the rear.

(at around 1h 50 mins) When Saint is tied to the car and the explosions are happening, his lower half catches fire. In the next shot, he is not on fire.

After Dave comes back from the hospital, the tissue in his nose switches sides after he comes into the apartment.

(at around 23 mins) When Castle grabs the motorcycle to chase after the gunmen who are chasing Maria and Will, the dead family member who'd originally been riding it is nowhere to be seen.

(at around 1h 7 mins) When they were transporting the money in the boat, Castle used a Claymore anti personnel mine to blow up the money. When the mine detonates, there's a big fireball. Claymore mines are filled with 100 metal balls, and do not explode creating a fireball. The explosion in the scene is not typical for a Claymore mine.

(at around 36 mins) After Frank is shot on the pier he later returns to his Father's house and retrieves his Father's guns, since it was a crime scene the police would have removed all the weapons from the scene and not left them for anyone to steal.

When Quentin is getting ready to set the pier on fire, he sprays diesel fuel (green cover on the pump) all around and lights it. Diesel is not very volatile - it does not change to a vapor easily like gasoline does. You can throw a match into diesel and it will usually just get snuffed out. Diesel is injected into an engine under very high pressure and through tiny nozzles so it atomizes into a very fine mist, and since it's injected into very hot (compressed) air, that combination of fine mist and heat is enough to cause it to vaporize and ignite. Diesel fuel just laying there won't do anything.

(at around 28 mins) The truck that is used to kill Castle's family (in Puerto Rico) has a front license plate. License plates in Puerto Rico are only displayed in the back of the car, as you are only given one plate for the car.

All glass in commercial buildings is tempered, and can not be cut with a glass cutter as shown.

(at around 24 mins) During the massacre at the Castle estate in Puerto Rico, when Maria attempts to escape with Will, she tells him to "run to the Jeep." It's a Chevy Blazer, but "a Jeep" is commonly used as a shorthand for an off-road car, not necessarily of a Jeep make.

(at around 10 mins) After Saint kills the henchman that was assigned to look after his son, Saint drops the gun on the stomach of the henchman only to have him jump as the weight of the gun hit his gut.

(at around 24 mins) After Castle shoots the gas tank, it blows up the henchman setting him on fire and you can see the fireproof mask and gloves on him.

(at around 27 mins) When the Blazer flips over, you can see the mechanism under the truck on the passenger side used to flip the truck over.

(at around 25 mins) As Castle and Lincoln fight, and Frank lifts the knife to Lincoln's face, right before Frank cuts him, you can see the tape across the face of where Lincoln is to be cut.

(at around 26 mins) Obvious stunt double when the Blazer starts to flip over.

(at around 52 mins) As the camera scrolls the partial view of Castle's ID file on the monitor of Spacker Dave's PC, the word "member" is misspelled as "memeber".

At 31.50 in, as the bad guys are leaving the pier, you can see the film has been flipped. The writing on the building is all reversed so it's reading back-to-front.

Around 32 minutes in, as the goons drive the red truck back past the dive shop, the shot is reversed and all text is backwards.

(at around 1h 7 mins) When Frank Castle detonates a bomb on board a Saint-owned drug boat, immediately before the explosion is the "whoosh" of a rocket. The audio clip was clearly from a missile impact, not a mine or bomb.

(at around 26 mins) When the Blazer flips over we see the crew standing in the background.

(at around 1h 6 mins) After Frank's car jumps the bridge during the car chase, you can see the jump harness used to protect the stunt driver from receiving any back injuries.

(at around 30 mins) When Castle is on his knees on the pier, you can see the outline of the blood squib underneath his undershirt.

(at around 1h 3 mins) When the guitar player, Harry Heck, plays the song he wrote for Frank Castle, you can see a microphone on the guitar.

(at around 22 mins) When Frank's wife Maria is walking with their son on the beach, she mistakenly tells him that a horseshoe crab is a sting ray.

(at around 1h 30 mins) In the "declaration of intent" monologue, Frank utters the phrase 'si vis pacem, para bellum' but mistakenly uses the word 'sic' ('as is') instead of 'si' ('if').