Continuity mistake: Carter and Cadet Haley enter the Stargate and we see them through the "puddle." When they come out on The Other Side, their positions are reversed.
Other mistake: Just after the scientists on an alien moon follow The Light into the forest there is a car behind them.
Revealing mistake: Even after Teal'c is dead, you can see in one shot that he is still breathing.
Other mistake: Carter says that the chance of depositing the heavy element inside the Katow sun while the element is en route is about 1%. However, hypothetically speaking, the actual chances would be infinitely smaller, in fact it would be near impossible. Simply consider the distance from earth stargate to the Katow stargate, the diameter of an average sun, and the time it takes for an object to travel through the gate (about 12 seconds). Taking the closest star to us (Alpha Centruri), at a distance of 4 light years, this means that the wormhole takes ~443ns (0.000000443s) to pass through the sun (using our sun diameter). Similarly, taking the diameter of the Milky Way as the distance to the furthest star in our galaxy, ~100000 light years, meaning the wormhole takes ~17ps (0.000000000017s) to pass through the sun. This means that the SGC would have to shut down the gate within a a maxmium of 443ns or a minimum of 17ps time gap. As we have previously seen, the stargate takes far longer to shutdown than these miniscule time lengths.
Revealing mistake: When Jack is asking the Martian where he got the idea for the show, you can see the camera light reflected in the Martian's glasses.
Factual error: In the scene where O'Neill and Maybourne are looking up NID flight plans, the plan viewed on the computer lists the destination airport as Minot Airport Base, but provides the airport code for McCarran International Airport (KLAS). It also lists non-existent runways, as in runway headings that do not exist anywhere in the world. (00:24:15)
Summit (1) - S5-E15
Plot hole: During the briefing at the Tok'ra base about the deadly symbiotic poison, Ren'al says that dying symbiotes release their own toxin which is just as deadly to the hosts. Yet in other episodes when a symbiote dies in the host's body, the host doesn't die, even without medical treatment. For example, the whole infected town of Steveston is just fine when all the symbiotes are killed (s06e05).
The Warrior - S5-E18
Continuity mistake: When Teal'c and K'tano are fighting and K'tano says "is that the best you can do", you see Teal'c's training staff on the ground and it's already broken, even though that hasn't happened yet. When Teal'c stands up, that's when K'tano breaks his staff.
Revelations - S5-E22
Revealing mistake: Just before Teal'c and O'Neill get to the engine room door, Carter can be seen hiding around the corner. (00:27:40)
Deliberate mistake: In the scene when the timer exceeds 38 minutes, said timer is displayed in big digits on a computer screen. There is a shot of General Hammond with the Stargate in the background. There is a pane of glass between the General and the Stargate. In the shot, General Hammond turns and looks at the gate, and then the camera's focus changes from the General to the Stargate itself. In doing so, a reflection of the timer in the pane of glass is also brought into focus. However the timer is displayed correctly when it should be flipped left to right as all text is when it is reflected in either a pane of glass or a mirror. On the DVD, the writers revealed that this was done on purpose so that the viewer would have a concept of the time running out even when the timer wasn't in shot. (00:17:30)
Continuity mistake: In a scene where Sergeant Walter Harriman tells General Hammond that SG-1 is ok, but Dr. Friesen is dead, Sergeant Walter Harriman is wearing the uniform of Major Davis (you can see "Norman Davis" written on left side of his chest). [His name was originally Norman Davis. At one point, Hammond refers to him as "Airman". This was misinterpreted as him being called "Harriman." Then, in the episode 2010, O'Neill calls him Walter. Thus, his name changed from Norman Davis to Walter Harriman. Still a mistake, but that's why.] (00:30:15)
Continuity mistake: When Jack is revived in the sarcophagus after being caught, the first shot of this his shirt is in perfect condition, but in the next shot of it, there is a knife hole in the shirt which disappears when he is being taken to the "anti-grav torture wall"
Continuity mistake: When Samantha Carter is locked in the storage room on deck 7 and she uses the plasma cutter to make a hole in the door, there is a fingerprint on her visor which appears/disappears between shots. (00:25:30)
Unnatural Selection (2) - S6-E12
Other mistake: When Thor reveals to SG-1 that the Replicators have reversed the time dilation device, he says time is moving at a factor of "10 squared" (100 times faster than real time). Carter says that in the hour that passed, 4 days have passed for the Replicators (which is correct), but then says depending on when they did it, hundreds of years could have passed. But that's not possible since that means years in real time would have passed. But the Asgard didn't set this trap years ago, just recently.
Disclosure - S6-E17
Plot hole: Senator Kinsey references the Foothold incident from season 3, yet only a few episodes before it was revealed that Kinsey could never have known about it because it was covered up under presidential orders and he especially was not in on it.
Visible crew/equipment: When O'Neill, Carter and Quinn meet Teal'c at the ship wreckage, the camera moves to focus on O'Neill. The shadow of a boom mic on the ground follows his path. (00:02:05)
Other mistake: When Jonas says he has flashes of what's going to happen (and no-one believes him), Teal'c says they have encountered many strange phenomena but no-one who could see the future. Except Jack and Teal'c had a whole "Groundhog Day" episode where, because they were stuck in a loop, they could see the future. Carter then says it goes against all the laws of physics as we know them, despite knowing time travel and other things that break the laws of known physics exists.
Revealing mistake: In the scene where Thor beams onto Loki's ship, as he stands there you see him turn his head. However, if you watch his reflection in the window behind him, his reflection stays facing forwards.
Visible crew/equipment: When Daniel is talking to Teal'c and the other Jaffa, at one point we can see a light reflecting screen reflected in Daniel's glasses, we can even see the silhouette of someone's arm and body in front of the screen. (00:20:05)
Continuity mistake: When Teal'c attacks the blonde Jaffa, the Jaffa has a staff weapon, but the shot changes when Teal'c hits the Jaffa and the staff has disappeared.
