Other mistake: When one of Jackson's crew raises his 35mm camera and takes a picture, there's no lens on the camera.
Visible crew/equipment: Throughout the movie, in the shots of the guys on the alien planet, the white reflector screens and film crew's reflections are visible in their sunglasses. (00:40:20)
Factual error: The military ranks for everyone but O'Neil are wrong. O'Neil is a Colonel (Full bird), Kawalsky is wearing the insignia of a Lt Colonel, but is referred to by O'Neil simply as Lt., when he should be called Colonel. All the others are wearing enlisted stripes (Ferretti - TSgt, but is credited as Lieutenant Ferretti), the others are also credited as "Lieutenant", but wearing enlisted stripes.
Audio problem: Right after Jackson has been dragged through the desert by the creature, it wakes him up and he says, "Get away from me," but his mouth never moves. (00:40:30)
Revealing mistake: In the scene where O'Neil is fighting Ra's bodyguard, the bodyguard uses claws and hits O'Neil's back, tearing his shirt and wounding him. But you can see Kurt's "wounds" and torn shirt right before he's hit by the bodyguard (a scene after Ra's bodyguard's claws are shown). (01:49:10)
Continuity mistake: When Jackson is in the meeting about the symbols, he circles the seventh symbol with a blue marker. In the next shot, look close and you can see that the blue circle around the symbol is gone. (00:18:20)
Continuity mistake: There is no necklace on Catherine's neck when she greets Jackson in the room with the cover stones (00:13:39). After they have shaken their hands, the necklace appears on her neck suddenly. Then it disappears again. Also, after Catherine has given the necklace to Jackson for bringing him luck before his departure, the necklace appears on her neck again when she is in the control room during their departure.
Factual error: When they first power-up the Stargate in the military facility (using Jackson's decryption), the thing surges to life, and electrical sparks spray out of overloaded connections all around the control room. This could only happen if there were no fuses or electrical breakers in the military's control system, which is a ridiculous notion for such advanced military technology. In real life, a powerful overload situation would instantly burn out fuses and trip breakers and the whole system would simply go dead (there would be no sparks). Showers of sparks are a common error in many science fiction and space fantasy films dating back many decades.
Continuity mistake: After the slave boy gets a cigarette from O'Neil, he reaches out to touch a gun, and O'Neil grabs it and scares the kid away. O'Neil is then holding the gun with the barrel pointing towards the door, but as the angle changes he is suddenly holding it at a different angle, pointing down to his right and away from the door. (01:05:30)
Continuity mistake: When O'Neill, Jackson, and Sha'uri have just entered the Stargate chamber, O'Neill throws aside his staff weapon and starts working on the bomb. Later, during the fight between O'Neill and the guard, an overhead shot shows that the staff weapon is no longer there.
Revealing mistake: When the crew is transported to the distant planet, there are three moons. They are all the same shot of our moon (the craters are the same), but each moon is turned differently than the other two. (00:33:15)
Continuity mistake: When the men are in the pit of water the man who says "Colonel it's us", his dog-tags change from on his chest to back several times between shots.
Continuity mistake: The bomb's countdown starts faster than a second between numbers change, then eventually gets to about 1 second/change, then goes faster, etc. Its speed keeps changing from shot to shot. Also, the numbers are inconsistent and don't match the time passed between shots of the same scene (i.e. one second later, the countdown can be 5 numbers down).