Revealing mistake: After Sayid stabs Sawyer, in the wideshot when Jack pushes Sayid away, as Sawyer lies with his right arm outstretched the knife is nowhere to be seen. In the next close-up, the large, long-handled knife is protruding from Sawyer's upper arm at about a 90º angle. Given the angle and position of the knife, it should have been seen in the previous shot.
Continuity mistake: When Sayid stabs Sawyer, in the close-up there are considerable blood stains on Sayid's white shirt, yet when Jack pushes Sayid off Sawyer all the blood has vanished. This continues to happen in all the following shots, when Jack tells Sayid to get his bag, and the amount and pattern of blood also significantly changes.
Continuity mistake: Just after Sayid has woken Sawyer up by throwing water in his face, there is a shot of Sayid from behind the tree Sawyer is tied to, and you can see a bit of Sawyer's hair. However, it is hardly wet, if at all, and when the camera cuts back to Sawyer his hair is drenched again.
Continuity mistake: After Sawyer admits to Kate that he doesn't have the inhalers, Sayid and he get into a tussle. In the first shot, the back of Sayid's white shirt is fairly clean as he is standing, but in the next wider shot the back is completely filthy - before he and Sawyer ever even hit the ground.