Speed (1994)

Revealing mistake: When Howard shoots the subway driver near the end, we see the driver collapse and die. Where did the damage from the bullets go? There's not much in the way of bullet holes or broken glass. Certainly an automatic weapon would've produced some damage.

manthabeat

Revealing mistake: When Jack is fighting Howard on top of the train, for a second or two, you can see a blue screen behind Howard instead of the regular background. Someone forgot to add the chroma key background in post. (01:44:05)

Revealing mistake: When Jack is under the bus attempting to dismantle the bomb, if you look closely, when the cable comes off the hook, you get a shot of Norwood and the Lieutenant standing on the edge of the van holding the cable - you can see that it's their stunt doubles standing there.

Revealing mistake: When Jack and Annie are about to slide out from under the bus, if you look closely when we see Annie hold on to Jack's back, you can see stunt wires visible attached to both characters. (01:29:55)

Revealing mistake: In the elevator scene, when Jack looks up standing on top of the elevator, you can obviously tell that he is in front of a rear projection. Notice the elevator ropes don't move one bit.

Revealing mistake: In the shot where Jack and Harry are descending a ladder to the stranded elevator, we get a good look at the elevator shaft and its surroundings. Upon closer inspection you'll notice how the lowermost section of the shaft is actually a mural - given away by the shadows cast upon it. (00:09:20)

Revealing mistake: A large crowd of onlookers is visible on the highway overpass in the background as soon as Tuneman props himself up in the driver's seat after crashing into the water barrels. (00:40:10)

Revealing mistake: When Jack is on the phone with Payne at LAX, a Suburban carrying Lieutenant McMahon and Norwood skids onscreen from between some orange cones. But tire tracks from earlier takes can be seen on the pavement. (01:10:00)

Revealing mistake: When Payne opens the money bag to see a dye bomb explode, he is wearing a transparent protective face shield (partially visible). (01:42:35)

Revealing mistake: At the off-ramp's red light Jack stomps on Annie's foot to keep the bus going, but she screams in pain before her foot actually gets crushed. (00:47:15)

Revealing mistake: The whole structure surrounding the elevator appears shiny and spotless, with the wires lacking a single spot of grease, revealing it's a set. (00:04:25)

Sacha

Revealing mistake: When Traven is walking back to his car before the first bus explodes, as the bus drives past him, you can see from the shadow it casts that the bus isn't driving straight on. It turns the corner behind his car. Obviously a prop bus is further down the street and that is the one that blows up in its place.

Revealing mistake: When Ortiz first sees Jack stranded beneath the moving bus, he lifts his head to tell Annie. But the pavement, as seen through the bus floor's opening, is completely motionless. (01:17:25)

Revealing mistake: There is a clear shot of Keanu Reeves' stunt double in the Bronco just before it parks on the highway's shoulder near the gridlocked traffic. (00:34:20)