Revealing mistake: In at least one scene at the Bada Bing, the neon sign reading "Satin Dolls" can be seen reflected in the mirrors. Satin Dolls is the name of the real strip bar where the Bada Bing scenes are filmed.
Knight in White Satin Armor - S2-E12
Revealing mistake: While Christopher and Furio are dismembering Richie Aprile on a meat saw, you can see that the blade of the saw is still, but the blood is splattering all over the place, and you can hear the sound of the meat saw cutting through flesh. (00:49:55)
Continuity mistake: During the scene in the office of Bada Bing, Pauli, Christopher, Tony, Silvio and Pussy are all together and the TV is on. Pussy is reading something and Christopher is lifting weights. In between shots, the weights change from Chris's right arm to his left and back again. It could be argued that he changes arms when the camera is off him, but there is one instance where it definitely happens too quickly for this to be the case.
Nobody Knows Anything - S1-E11
Character mistake: When Tony tells Dr. Melfi he feels as though a safe might fall on his head, she replies, "a feeling of pending doom." A woman of her intellect and education should know the proper word is "impending." "Pending" means something awaiting a conclusion. "Impending" means about to occur.
For All Debts Public and Private - S4-E1
Continuity mistake: Tony throws the newspaper at his son and it lands with a corner folded on the cereal bowl. From the opposite angle it is laying straight on the table.
Continuity mistake: When Meadow is looking mournfully at the Scrabble board, she sees that Jackie laid "the" using the letter e from "oblique" that she laid. However, when they were playing the game, the only word after oblique that Jackie laid before leaving was "ass".
Other mistake: In season 5 episode 7, Tony is talking about JFK, and said he was in grammar school when it happened. However, in this episode Tony celebrates his 47th birthday. He was probably born in 1960, so he would have been no more than 3 years old and not in grammar school when JFK was president. (00:26:36 - 00:38:02)

Visible crew/equipment: As the ducks fly away, a crew member can be seen stamping their foot in order to scare the ducks. (00:06:40)
The Legend of Tennessee Moltisanti - S1-E8
Continuity mistake: When they drive in the Lexus, around 33 min into the scene, you can see the headrest on the driver's seat moving up and down as the shot changes from him to Tony and back. Happens several times. (00:32:55)
To Save Us All From Satan's Power - S3-E10
Continuity mistake: When Tony sees Jackie Jr. getting a lap dance, the dancer has her top pushed up. After Jackie pushed her off and she moves past Tony, her top is down without having time to move it. (00:29:10)
The Fleshy Part of the Thigh - S6-E4
Continuity mistake: The card with the proverb stuck on the billboard keeps swapping positions depending if the angle is medium or close.
Irregular Around the Margins - S5-E5
Visible crew/equipment: Visible crew reflected on car's mirror when Chris opens the door.
Irregular Around the Margins - S5-E5
Continuity mistake: When the car that Tony and Ade are driving flips over, the back lights on the car die out. But in the last shot of the car the back lights are back on.
Audio problem: In the first long shots of Visiting Day playing at the club, the lead vocal is heard, but the singer is standing well back from the mic and does not appear to be singing.
Continuity mistake: When Meadow is driving Janice's car, Janice's right arm moves around on the window sill from shot to shot, and the cigarette Janice is smoking gets longer instead of shorter as she smokes it.
Continuity mistake: Tony makes a toast at the dinner table in front of Carmella and Anthony. Watch Tony's wine glass during the toast, the amount of wine in the glass changes dramatically from shot to shot. (00:21:45)
Continuity mistake: When Silvio Dante is talking to Richie Aprile, from a back shot Silvio rests his head to the back but in the next shot it's straight and down.
Continuity mistake: When Hesh and Massive Genius are talking on the porch, Hesh is leaning forward and picks up a glass of ice tea. A second later, in the next shot he is sitting back in his chair, and is no longer holding the glass.
Continuity mistake: The size of the hole made by Tony Blundetto on the wall keeps increasing and decreasing all the time.
Watching Too Much Television - S4-E7
Visible crew/equipment: When Furio is at the Sopranos' to pick up Tony and tells Carmela he'll be waiting in the car, a crew member can be seen reflected in the door glass as Carmela closes the door. (00:38:55)
Answer: That's not Jimmy, just a look-a-like. Jimmy's short and stout, the guy in "Christopher" episode is tall and medium built. The hair is also different.