Revealing mistake: While Indy and Marion are in the Well of Souls, and they encounter the snakes, Indy falls to the ground only to be confronted by a hissing Cobra rearing its head. Look carefully and you'll see the snake's reflection on the safety glass between it and Indy. Briefly you can also see the torch's reflection while he's waving it around. You can also see Marion's reflection when she falls in later on and is face to face with the cobra. [This has been corrected in the new DVD set. You can only see it if you have the original VHS. I think it's visible in the "making of" on the DVD as well.]
Continuity mistake: When Cheryl is running through the woods, she is wearing slippers that stay on up until she reaches the cabin door. However, in following shots, she is shown barefoot, and when Ash opens the door her foot is dirty as if she'd been running barefoot the whole time. (00:28:05 - 00:29:10)
Factual error: Regardless of how bad an attorney he is, Ned Racine must surely know that his acquittal for murder is a shoe-in. It's very doubtful that the prosecution would have even held out for remand in his case, and in fact they probably would not have even charged him in the first place. The fact that his fingerprints are on Edmund Walker's glasses is irrelevant. He and Racine were seen in public together, notably in the restaurant, and he freely admits to being in Walker's house. He could have handled Walker's glasses on any one of these occasions. The conversation Racine has with Ted about building the firebomb cannot be used in court, as Ted fires Racine as his lawyer at his second meeting; everything from the first is covered by attorney-client privilege. Maddy obviously isn't around to give evidence, and the yearbook entry Racine finds throws suspicion on her (and away from Racine) immediately. There are no witnesses and no forensic evidence, in fact there is nothing to support the prosecution case except a vague suspicion based upon his having had an affair with the widow-to-be. No court in the US would entertain the case for a minute.
Factual error: Then, as now, every recruit reporting to boot camp would be tested for illegal drugs, first by a urine test and then by a broad spectrum blood test in the case of a positive result. There is no reason for Elmo to try to hide his stash when the recruits are told they are to be tested - he is going to come up positive anyway. He may as well just say he has changed his mind and walk away. He is entitled to do that any time up to ten days after he signed on, and it happened a lot in real life!
Factual error: When the Titanic sinks all six dwarves and Kevin end up in the sea clutching a lifebelt. The water in which the Titanic sank was freezing - that is how most of the casualties died, by freezing, not drowning. In water like that you'd be lucky to stay conscious for more than a few minutes. Despite this none of them show the slightest effect of the cold. Maybe the dwarves have some 'magical' ability to withstand lethal cold, but Kevin doesn't even react to being plunged into freezing cold water. He'd be screaming in pain, but he doesn't even show the slightest sign of discomfort.
Continuity mistake: When Mommie is cutting Christina's hair it keeps on changing from long to short several times.
Factual error: Frank, Archie and Snowy are all rural boys from New South Wales, but they all play Australian Rules football expertly. In 1915 Australian Rules was completely unknown outside of Melbourne. In a time before television or film they wouldn't even know what the ball looked like. In fact the game was only established in Sydney, Perth and Adelaide in the 1980s, and is still not terribly popular there. There is no way in the world three people from outside the state would know how to play the game, let alone with such skill.
Visible crew/equipment: When the boy takes the boat out for a ride by himself and is riding it around in circles, you can clearly see the helicopter's shadow in the center of the circle.
Revealing mistake: When Bond throws the dead pilot out of the helicopter, you can tell it's a dummy as its arms and legs bend at impossible angles.
Continuity mistake: When Snake kills the wrestler he falls forward shoulders forward, next minute his arms are over the ropes, next minute his arms are in a different position again - quite active for a dead man. (01:16:55 - 01:18:10)
Factual error: Another flag gaffe: The Canadian flag in the 1920s was either the red ensign or the Union Jack. The Maple Leaf only became the national flag in 1965.
Revealing mistake: In one scene just before the attack on a big Hunter the young captain (Jürgen Prochnow) is sitting with his charts. Beside him he has got a glass of beer standing. The sub lurches heavily right and left in the hard weather, but the surface of the liquid stays the same.
Visible crew/equipment: After Arthur drinks from the Grail and goes to visit Gwinevere at the convent and she gives him the sword back, he paces around her chamber- you can clearly see the film crew reflected in his armor.