The size and shape of Jack's wound at the neck in front of the mirror change between wide and close shots.
After the fight between the Man in Black and Jack, when the rain stops and Kate, Hurley, and Sawyer appear, the ground around them changes from wet to dry repeatedly. Moreover, during the fight in the rain, several nearby cliff faces collapse, but, when the sun comes out, the cliffs look no different than they did previously.
When the Man in Black is looking down at the boat on top of the cliffs, there is is no blood on his face, but when he turns to Jack, he has blood running down his face from his nose, which then disappears again during the fight.
While Jack is walking through the bamboo, the blood from his nose appears and disappears.
When the Man in Black and Jack are fighting on the cliff, MIB stabs Jack a few inches below the armpit, but when the fight is over and Kate is helping Jack, he pulls up his shirt to show the wound just above his belt.
However, immediately after the armpit scene, MIB can be seen having stabbed Jack in the abdomen, too.
The vending machine that Sawyer uses at the clinic contains the numbers G22, G23 and G24 on the same row as E6 and below row 'D', suggesting that these have been stuck over the original numbers.
This was done in order to make the Apollo bar that Sawyer buys sit in column 23.
This was done in order to make the Apollo bar that Sawyer buys sit in column 23.
After Ben throws Sawyer the walkie-talkie at the cliffs, the shot in which he says "If the Island's going down, I'm going down with it" is flipped, as is visible from the wounds on his face and the strap of his bag.
When Jack climbs out of the pool before walking through the bamboo, his audio transceiver is clearly visible under his shirt at the top center of his back, multiple times.