Character mistake: When Gibbs first looks at the victim's body and sees his rank, he incorrectly refers to him as a Lieutenant when the rank is for a Captain.
Other mistake: When we see McGee get a match for the terrorist, the picture of Ari that we see has been shown many times before in the search for his identity.
Ssiscool
Visible crew/equipment: When Gibbs and Ziva are in the "safehouse" Ziva set up for Ari, a crew member and his boom microphone are seen on the left of the screen, right before Gibbs climbs the ladder to remove the hidden camera spying on them. (00:30:10)
JackAndtheBoxContinuity mistake: They say the suspect was dishonorably discharged in 2008. A minute later in the episode they say he was dishonorably discharged in 2010. (00:10:50 - 00:11:55)
ExpatScott
Continuity mistake: When Tony shows Chandler's boarding pass to McGee for photo evidence, Tony's hand moves from holding the upper edge to the lower edge. (00:04:15)
Cubs Fan
The Truth Is Out There - S1-E17
Revealing mistake: Gibbs finds a bunch of cash hidden in the victim's speaker. "For Motion Picture Use Only" is printed on them.
ploypContinuity mistake: 5-4: Identity Crisis. When Ziva is speaking with McGee her lapel changes from being turned up and laying down.
BoobraSilver War - S3-E4
Visible crew/equipment: When in Ducky and Jimmy are in autopsy alone, there is a cameraman in the reflection of the body cooler wall. (00:18:15)
Nicholaus CumminsContinuity mistake: When he hands Tony the autopsy report, Ducky has hair falling over his forehead, then combed back, then over his forehead again repeatedly from shot to shot. (00:07:15)
Visible crew/equipment: In the scene where Tony approaches the Mallard residence by car for the first time, there is a stage light, complete with filter(?) on the balcony. (00:13:50)
Yankee White - S1-E1
Factual error: Air Force One landed in Wichita, Kansas. The local coroner claimed Jurisdiction for Wichita County. The city of Wichita, Kansas is in Sedgwick County, in southern Kansas. Wichita County, Kansas is in western Kansas, about 250 miles from the city of Wichita. (00:05:40)
Untouchable - S3-E20
Continuity mistake: The camera pans across a line of several anime plushies. When the shot then goes wide, several of the plushies have either been re-arranged or removed completely, including a pink plush and the Kyogre plush. It also seems as though there are two Miroku plushies in the scene as well, one near the middle and one off to the side of the left pillow. (00:04:10)
Character mistake: When Kate mentions James Bond, and DiNozzo lists the actors who have played him, he forgets Timothy Dalton. As a self-proclaimed film buff, that's not a mistake he would make.
Cubs FanOther mistake: Season 5, Episode 12, "Stakeout": The picture on McGee's camera phone is just wrong. It shows not just the man in front of him, but it also shows a hand, holding a camera phone - McGee's camera phone. In other words, the phone is showing a picture of itself and the man, instead of just the man. (00:40:25)
Revealing mistake: When DiNozzo is watching the ship through the binoculars at the beginning, the film is run in reverse. The sailor smoking on the deck is the giveaway, as the smoke he's blowing is going into his mouth. (00:00:15)
Visible crew/equipment: When the voice activated 4x4 is driving back, you can see the camera's shadow reflected onto the tyre in the close ups of it. (00:00:40)
Ssiscool 
Continuity mistake: 7.05 - Code of Conduct. Gibbs and Tony go to question a marine who is exercising. The sweat stains on his shirt get much bigger and smaller, as well as change shapes, throughout the interview. (00:20:35)
ployp
Continuity mistake: In the Episode "Sharif Returns" When Ducky shows Gibbs the eye in the gladd vial, it alternates between being completely submerged in the fluid to sticking out the top.
Boobra
Chosen answer: "Policing your brass", means to pick up your expended shell casings, after firing your rifle, or pistol.
pross79