Continuity mistake: When Bond is flying over China and landing on the sea by Scaramanga's island, you can see that his plane has two floats - one on either wing. But in the shot where he is heading for the beach, it is clearly seen that the left float has gone! (01:28:40 - 01:30:55)
Other mistake: In the original version of the film there's a mistake in the opening credits where Colin Blakely's name is misspelled as Colin Blankey.
Continuity mistake: The people inside the elevator disappear in the wide angle. (01:57:21 - 01:57:51)
Continuity mistake: The small plane's pilot identifies the aircraft as 232Z. But in the exterior shots, the aircraft's identification is N9750Y. (00:35:00)
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.
Continuity mistake: After the general is killed, there's a close-up on the figurines. Two are broken with just the feet left, the third, the rightmost, at the waist. When the second victim was murdered, we saw the killer break just its head off, the statue to the right of the halved one. The following shot shows the statues in that order, with the addition of third broken one in rightmost position. (00:34:15 - 00:42:15)
Revealing mistake: When Butt falls behind the suitcases, a mattress to soften the fall is visible.
Other mistake: When Hyman Roth's assassin runs at the airport, he is turning around with one (of two) bullet holes already in his jacket before the sound of any gunfire. (03:10:50)
Revealing mistake: When the parking lot building collapses, check the right side where the cars are. All along the ground level there's a rectangular strip where the film of the miniature building was pasted on top of the film with the real-sized parked cars. Note how all the debris falls behind that strip, it never falls on top of the cars, as if there was a weird black hole of some sort. (01:37:54)