Deliberate mistake: If you pay extremely close attention to the scene of all of the Decepticons responding to the small Transformer's message regarding the location of the Allspark, notice that the shot of the police car and the fake helicopter pilot are duplicate shots used earlier in the film.
Deliberate mistake: When Agent Hoffman writes the letter to Amanda, he puts the envelope so her name is pointing down, yet when Amanda opened this drawer in Saw III her name was at the top. The director had to do this or it would have revealed Hoffman was the new apprentice all along.
Deliberate mistake: During the scene where Carlos and L.J. are searching the motel, L.J. sees a zombie which turns out to be a reflection in a wall-length mirror. L.J. shoots, breaking the mirror and realizing his mistake. But, if he had been standing in front of the mirror as shown, he should have seen his own reflection standing there as well. This was done as an homage to a similar encounter in the original game. (00:24:20)
Deliberate mistake: At the end of the movie, where the girls chase stuntman Mike, they drive the upper dusty road. When their car is shown front outside angle, there's a lot of dust rising from the camera crew's car. But when the camera angle gets into their car and shoots strait ahead - the dust is all gone, the air is perfectly clear.
Deliberate mistake: In the facial morph, the faces don't come anywhere close. The face was morphed with no feature of either resembling the other. The only matching features were the hair and neck which were not touched by the morph. The midpoint of the shift wreaks of Photoshop-like effects (softening of the face alone). (00:41:50)
Deliberate mistake: After Bert is shot in his car, Bobby pulls up beside him and just after Bobby shouts, "Pop, pull over!" the first time, the next tight close-up of Bobby's face is a flipped shot. Note his earring and the scar on his upper lip have switched sides. (01:17:00)
Deliberate mistake: When John crashes the car against the elevator room, the cables he and the woman hold on to are clean, when they should be greasy - thus allowing for them to hold safely.
Deliberate mistake: A stunt double for 47 got hurt on camera and yelled, very obviously. Right after the sword fight on the train the last man 47 is fighting continues the fight hand to hand under the tracks. Timothy Olyphants stunt double throws a punch and he grips his hand, yells and his face comes into screen for a moment. Next shot, Timothy Olyphant throwing his own punches.
Deliberate mistake: So right before the containment team seal up the window with the tarp, the SWAT is shown having police dogs. The virus (which came from a dog in the first place) can be transferred through saliva. The SWAT obviously overlooked the fact that the potentially infected people who might escape could be bitten by the dogs.