Revealing mistake: During the fight scene in the belly dancer's room, Bond spins the bald guy around to avoid being hit by a chair. When the bald guy gets hit in the back with the chair, you can see a large rectangle of padding under his jacket.
Revealing mistake: In scene at the brothel, with the senator and the dead prostitute, the supposedly dead body is breathing in the last shot of her, just after Tom Hagen says "it'll be as if she never existed". (01:15:30)
Revealing mistake: Watch carefully as the statue falls on the bartender. It barely touches his chest and rests on his left thigh. As the bartender slumps dead you can see a wide open gap between his whole upper body and the statue. Even if it crushed his thigh it would not have killed him so quickly. When the bartender slumps down the statue rocks freely as he brushes against it; obviously a styrofoam replica.
Revealing mistake: After the crazy man cuts his own hand, he laughs and waves the knife. Watch carefully and you can see the hose behind the blade the blood came through. (00:13:40)
Revealing mistake: When Mr. Green pulls out of 28th Street, we see him disengage the "Dead Man's Feature" (by pressing down on the throttle with his hand). However, he does not actually move the control lever to make the train move. In that position, the train is at "idle" and will not accelerate.
Revealing mistake: In the office tower after the quake there is a panic and workers rush down the stairs only to find them fallen away. After two women fall to their death a man is left hanging on a girder, but falls onto a giant piece of glass. Look at the top of the frame and you will see the airbag shooting our from under it.
Revealing mistake: When Pinback is hanging from the lift, just before he decides to undo the bolts, you can see a piece of wood supporting his back. (00:43:00)
Revealing mistake: When the co-pilot gets sucked out of the plane, it's obviously a dummy.
Revealing mistake: When Gittes visits the orange grove and crashes into the tree, you can see that a steel plate has been placed around the tree to protect it.
Revealing mistake: Oliver Reed heroically pummels a venomous snake made of rubber (therefore invulnerable to his heavy hits). (00:58:30)
Revealing mistake: When Butt falls behind the suitcases, a mattress to soften the fall is visible.