Revealing mistake: When Bond is on Goldfinger's plane - if you watch closely when it shows the external view of the plane in the sky you can see the plane is a model with two wires holding it up. The model plane's design and configuration are also quite different in mid-air. (00:54:20)
Revealing mistake: When headshots are shown of Bond inside the Aston Martin at the Auric Factory, and when he drops Tilly off at the gas station, you can see the three holes left in the headliner of the car where they have removed screws for the interior sun visor. (00:37:50)
Revealing mistake: When Bond's car crashes at the Auric factory, and the Mercedes comes to a stop, you can see the cut edges of the colored paper covering the headlights of the Mercedes. (00:45:50)
Revealing mistake: When Bond crashes his Aston Martin into a wall, the roof of his car has become magically reattached. (00:46:35 - 00:49:55)
Revealing mistake: When the small jet taking Bond to Washington is shown taxiing away from the assembled VIP the engines are not running (no exhaust) and one can faintly see a tow cable pulling the plane to the right.
Revealing mistake: The rear projection behind Bond as he is driving through Geneva doesn't match the scenery outside his car.
Revealing mistake: Before Goldfinger is sucked out of the plane, the flying cushions (superimposed on a chroma) magically vanish.
Revealing mistake: When Oddjob is killed and falls face-down, he turns his head to the left a second before he smashes it against the floor.
Revealing mistake: When Bond grabs a huge stick to attack Oddjob, the first wide shot behind Bond is of a very obvious stuntman with a square face and a prominent jaw. Stunt also visible after Bond jumps and grabs Oddjob's neck, when he is launched against the wall.
Revealing mistake: When Oddjob throws his hat at the statue and the head comes off the head falls on top of the arm and breaks it. Obviously this was not meant to happen as there is a quick edit in the film before the arm falls completely off (notice the trees behind the statue suddenly freeze).
Revealing mistake: When the CIA guys are following Odd Job to the airport in "Kentucky" there are several indicators that show they are in Florida. One is a big sign that says Opa Locka, which is north Miami.
Revealing mistake: Bond's unconscious body falling out of the car at the end of the car chase is obviously sped up.
Revealing mistake: As the laser cuts through the table towards Bond, the line where the cut is to appear is visible.
Revealing mistake: When they're in the barn, Bond and Pussy take turns tossing each other in the hay. On her second attempt to throw Bond, he reverses it and throws Pussy. After the camera looks to where she will land, you can see the distinct outline where she had been thrown before.
Revealing mistake: When Oddjob throws his hat at the statue and the camera cuts a close up of it, as the hat goes by the head, you can see the seam (in a freeze frame) where the head is propped up by the filler used to disguise the break. Also, the brim of the hat where the blade is, passes about two inches above the break. Therefore, were it possible, the brim doesn't cut the statue.
Revealing mistake: When the car containing Goldfinger's henchmen explodes after careering down a hill after spinning on an oil slick, look at the car and you can see that the back seat is empty.
Revealing mistake: At the beginning of the film, Bond shoots his rope gun to climb over the wall. If you look closely, the rope he shot didn't even come out of his gun. It comes from off the left side of the screen. Very visible in slo-mo, or paused.
Revealing mistake: When Bond is at the hotel at Miami, in several scenes you can see that film was shot at a hotel, and then the editors placed the card game opponent's figure in the film. The filming of the figures is a lot clearer and crisper, while the background looks like a homemade film.
Revealing mistake: "Q" says Bond has to activate the homing device by pressing it, but he doesn't press it, he pulls it back.
Revealing mistake: In Fort Knox, after Oddjob cuts the cables with his hat, he and Bond fight and Bond smashes a metal bar against him. Sean Connery's stunt double is very noticeable because of his longer and bulkier hair.
Chosen answer: They're not. Q was just indicating to Bond that these were the wing machine guns, he wasn't stating which was which.