(at around 1h 20 mins) When Hoffman is burning the Jigsaw evidence, you hear the click of the lighter as he opens it, he then drops the lighter into the gasoline on the ground, however you also hear the lighter closing again, though the lighter clearly never got into Hoffman's hands again.
When Bobby is trying to save Suzanne, he receives three sets of punctures in his sides. Later when he is trying to save his wife by crawling up the chains, the puncture marks disappear and then reappear.
When Officer Matt Gibson is searching for Hoffman, Gibson and the SWAT Team have their guns drawn, but in the next scene Gibson cycles the slide to put a bullet in the chamber, no cop would unload their gun and then load it again while searching for a criminal.
During the "Public Execution Trap", when Brad is clipped by the saw, you see blood on the edge of it. However, when the angle of the camera changes, the saw is clean. When the angle switches again, there is blood on the saw.
Officer Rogers spots the note for Officer Matt Gibson from Hoffman and the "Reverse Bear Trap". When he calls Gibson over, he has his arm up and resting on the door frame. When Gibson looks into the room, Rogers lifts his arm again.
When Gibson asks Jill if she knows who the man in the picture is, he is holding the picture in his left hand. When the camera cuts it is now in his right hand. He's also reaching between different bars.
After Bobby fails to save Nina, he has a large amount of blood spatter from her on his shirt. In the next scene, however, there is a lot less blood on his shirt, and it's splatter pattern isn't the same.
During the time in which Jill Tuck leaves the police station, she approaches the tricycle, during the change of angles there are tire tracks and footprints, in another angle there are none; the snow is smooth.
As Evan is tearing himself away from the car seat, you can see his back muscles only have a little bit of blood on them. When he crashes at the end of the scene, his back muscles are suddenly dark-red and saturated with blood, despite looking different just a few seconds prior.
When we see the "Reverse Bear Trap" at the start of the film, there is a small amount of blood on the trap from when Hoffman was in it. Later, when it's left for Gideon, there is a lot more blood on the trap. The device is nowhere near any other victims for their blood to spill on to it.
When Officer Matt Gibson is talking to Dr. Adam Heffner regarding if one of the victims has a cavity he wants to know about, the body bag is open. When the camera cuts to Gibson walking over to the door, the bag is done up instantly.
Officer Matt Gibson agrees to give Jill Tuck immunity in exchange for her testimony against Hoffman. However the police department doesn't have the authority to grant immunity, immunity can only be granted by the district attorney's office. The police are not allowed to promise a suspect immunity unless they have first cleared it with the DA's office. They can tell the suspect that they will recommend that the DA grant them immunity if they haven't yet spoken to them but they have to make it clear that it is not ultimately up to them.
When the IA tech is trying to track down Hoffman's location by hopping through all proxies until it can find the real IP address, the ipconfig output of the tech's computer is seen in the background. When displaying the name of the IA network in the ipconfig output, that configuration property label is misspelled as "Desciption" instead of "Description".
Hoffman's stitches disappear as the film progresses. This is due to the fact that the events of "Saw 3D" take place two months after the end of Saw VI, and flashes back a couple of times at the beginning of the film to establish continuity.
There are two ways Nina's trap could have been easily solved. Bobby could have either used one of the many objects around the room to knock her unconscious and remove the key, or he could have put her hand over her mouth with the string between his fingers and pull it out that way.
(at around 21 mins) In the "Horsepower Trap", we can clearly see that the arms that are about to be ripped out from Dan, are in fact already "ripped out" and just hang there, waiting to be dragged by the car.
During the ending montage, when the "Saw III" footage of Lynn Denlon's surgery on John Kramer appears, a very quick reveal of a pair of fingers tossing fake blood onto her face appears from the left side of the frame. However, this mistake was not present during the original sequence in "Saw III".
When Hoffman gets out of the body bag at the police station, he kills the coroner. He then hides by the wall next to the door as the second coroner walks in. The camera cuts and Hoffman is now standing in front of the second door, three feet away from where he was standing before.
When Hoffman inserts the metal rod in Jill's mouth through the front of the "Reverse Bear Trap" he then tightens three bolts with a spanner. However it is clear that only one rod is in place. When the device then snaps open we see a total of nine rods on Jill's upper and lower jaws.