Source: http://www.moviemistakes.com/best.php
1 Star Wars When the stormtroopers break into the control room, watch very carefully and you will be able to see a storm trooper nearly render himself unconscious by smacking his head off a door frame. This is now so notorious that on the new DVD there's an audible "bump" when he hits it.
2 Commando One of the most blatant mistakes ever committed to film. The yellow Porsche is totally wrecked on the left side, until Arnie drives it away, and it's fine.
3 The Rocky Horror Picture Show The criminologist describes the events of the movie as taking place "on a late November evening". In the very next scene, Brad and Janet are driving in Brad's car, and President Richard Nixon's resignation speech is playing on the radio. Nixon resigned in August of 1974.
4 Gladiator After the battle with the Germanians, the next morning after the tavern, he is walking in the army camp and he feeds a horse a piece of apple. If you look closely between Maximus and the horse, there is a crewman wearing a pair of blue jeans.
5 Harry Potter and the Philosopher's Stone When Harry, Ron and Hermione rush to Hagrid after the end of the year exams, and Harry is saying something that ends with, "Why didn't I see it before?", Hermione is mouthing his lines.
6 Charlie's Angels When the Angels are fighting the "Creepy Thin Man," right before Drew Barrymore lifts up Lucy Liu to spin her around and kick the thin man, to get Lucy's attention, Drew hollers out "Lucy!" even though Lucy Liu's character's name is "Alex."
7 Terminator 3: Rise of the Machines One of the most blatant mistakes ever seen onscreen - in the scene where John & Catherine are in the hangar at the runway, the Cessna's tail number is N3035C. When the plane is shown in the air, the number is N9373F. When they land, the tail number has changed back to N3035C.
8 The Matrix In the scene where Agent Smith is interrogating Neo, after Smith has sealed Neo's mouth shut and he is backed into the corner, when the camera cuts back to Smith you can clearly see a reflection in his glasses of Neo still sitting down in the chair.
9 Spider-Man In the scene where Mary Jane is being mugged by four men, Spider-Man throws two of the men into two windows behind Mary Jane. Then the camera goes back to Spider-Man beating up the other two guys. When the camera goes back to Mary Jane the two windows are intact.
10 Black Hawk Down Near the end of the movie when the convoy is heading back to the Pakistan Stadium, a Humvee stops briefly to allow a man to walk across the street with a child in his arms. When the shot changes and the Humvee begins driving again, a crew member or cameraman is seen inside the Humvee wearing a white shirt. All of the men who entered the Humvee were wearing fatigues.
11 Harry Potter and the Chamber of Secrets At the beginning of the scene near the end of the movie with Lucius Malfoy fuming at Dumbledore in his office, Malfoy's hair is fanned back behind his shoulders. The lighting in the room illuminates the back of his neck, where you can see his real, short brown hair.
12 The Lord of the Rings: The Two Towers Merry and Pippin were bound when taken by the Uruk-hai, and the bonds weren't cut until after they managed to escape during the fight. Yet, when the horse almost crashed down on Pippin, he had his arms spread out up near his face, not bound, even though they weren't cut until later. In the next shot, his hands are bound again.
13 American Pie In the bedroom scene the girl is holding a clear cup full of beer. The camera goes off her and when it comes back she is holding a blue cup. The camera goes back off her then on her and the cup is clear again.
14 Titanic The lake that Jack told Rose he went ice fishing on when she was threatening to jump is Lake Wissota, a man-made lake in Wisconsin near Chippewa Falls (where Jack grew up). The lake was only filled with water in 1918 when a power company built a dam on the Chippewa River, six years after the Titanic sank.
15 The Lord of the Rings: The Fellowship of the Ring In the scene where Sam and Frodo are in the field with the scarecrow, you can plainly see a car cruising past in the distance, from right to left. Further comment - there are two different shots which show the car moving from right to left. One starts at the top right distance, and in a shot a few seconds later the car has travelled down the road a bit and is more easily visible. Complicating matters is that the dust thrown up by the car looks similar to smoke from a chimney in the right distance, making some people think it is just the chimney. But chimneys don't move, and the smoke from the chimney is separate from the moving vehicle. [It is deleted on the DVD, but you can still see an obvious bit of image fakery on the hill just left of the smoking chimney. One can see the hill, tree, and surrounding area move up and down and shimmer slightly where someone has done a cut and paste to cover up the auto. The "car inclusive" scene appears on the National Geographic documentary Beyond the Movie The Lord of the Rings: The Fellowship of the Ring. Also, watch the music documentary on the extended dvd - when it shows this scene the car is still in it. Bizarrely, in his commentary Peter Jackson said he never saw a car and doesn't know what people are talking about, but the production/post-production team say in their commentary that despite not thinking anyone would be able to see it, they took it out anyway.]
16 X-Men 2 In the end, when the President is visited by the X-Men, he receives a blue binder, which is laid in front of him on the table. When they have left, you see a shot including the President's desk, and you can see that the only thing he has on the table are some sheets of paper, stapled in the upper left corner, opened up. Then the shot changes to a close-up of the President, and then back again, and you see the blue binder in front of him, closed, and the papers have disappeared.
17 The Lord of the Rings: The Return of the King In the second half of the film, Frodo has a scar on his lower right cheek, close to his chin. Many times throughout the rest of the film the scar changes position and size on his cheek and also from his right cheek to his left cheek (most obviously on the slopes of Mount Doom when Sam is cradling his head).
18 Top Gun At the end, a victorious Maverick is hoisted on the shoulders of the guys. As he goes up, he isn't wearing sunglasses. His head goes out of the shot, and when he comes down, he's wearing a pair.
19 Raiders of the Lost Ark While Indy and Marion are in the Well of the Souls, and they encounter the snakes, Indy falls to the ground only to get confronted by a Cobra rearing its head and hissing. Look carefully and you'll see the reflection of the snake on the safety glass between it and Indy. Briefly you can also see the torch's reflection while he's waving it around. [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.]
20 The Matrix Reloaded During the scene where Neo is talking to Agent Smith in the park area where Neo was talking to the Oracle, there is a close-up on Agent Smith's face. In his sunglasses you can see a bright white screen to reflect the light onto the faces of the actors. This isn't visible in any non-reflected angles.
21 Ocean's Eleven Linus and Rusty are standing in the Botanical Garden at the Bellagio going over Linus' observations. Rusty has a cocktail glass of shrimp in hand. When they change angles he has a plate in his hand...change back, glass.
22 The Wizard of Oz In the beginning while Dorothy is still on the farm, she walks along the pig pen fence and then falls in. When Bert Lahr picks her up out of there her dress is perfectly clean.
23 Die Another Day In the final fight scene on the plane between Jinx (Halle Berry) and Agent Frost (Rosamund Pike) Jinx is slashed across her stomach, drawing blood. In a later scene when Jinx and 007 are pouring diamonds over one another in the hut on the cliff her stomach is unblemished.
24 Attack of the Clones When Amidala & Anakin are eating and he cuts her a piece of the fruit and "floats" it back to her, the bite appears in the fruit a split second before she actually eats it.
25 Terminator 2: Judgment Day The T-1000 punches his body through the window of a helicopter to get inside. An instant later, the hole in the windshield is gone.
26 Jurassic Park In the scene where the tour trucks are stopped outside the Tyrannosaur paddock, we are shown a goat in a cage (inside the paddock) that appears to be at the same level as the road (outside). However, when Dr. Grant and Lex go over the wall, the ground is several stories down.
27 Beauty and the Beast In the 'Gaston' song sequence, near the end, Gaston is sitting in his huge antler chair with Lefou. In the wide shot, there is a bear rug behind the chair. The camera does a close up of Gaston, then in the next wide shot, the chair is on top of the bear rug. Also, after this, Gaston gets up off of the chair and in the next shot, both the chair and the rug disappear completely.
28 Willy Wonka & the Chocolate Factory In the beginning of the movie, when the candy store owner is singing the candy man song, there's a spot towards the end of the song were he opens up his counter to let all the kids in. Watch the little blonde girl as she gets wolloped in the chin by the counter.
29 Pearl Harbor In the scene where Rafe is fighting for Britain his plane gets hit. As it goes down into the water, it is day. Later when they show him swimming out of the plane and to the surface, it is night.
30 Chicago In the final scene where Roxie and Velma are dancing in the concert hall, Roxie is on the right and Velma is on the left. When they jump around to shoot their names into the lights, they have swapped sides.
