Continuity mistake: When Stallone stops the bad guys in the semi full of cocaine, they fly through a windshield that is apparently made of plate glass, and not the safety glass found on almost every other vehicle windshield on earth.
Continuity mistake: When Tango and Cash are playing the "good cop, bad cop" routine with Requin, the tape on Requin's mouth is almost off, but in the next shot the tape is OK.
Other mistake: Their big 4x4 at the end is really a two wheel drive. When they make the big jump with the fire all around them you can see the front end in the light. There is no front differential, just two big A frames.
Continuity mistake: When Stallone catches Tango with his sister, he sees a stranger (the Chief) in the screen door in the background. He jumps forward into the door taking it with him, along with the stranger. The shot then shows the door get pretty smashed up, falling apart as they both hit the floor heavily. The next shot sees Stallone picking up a perfectly intact door off a crushed Chief.
Continuity mistake: Towards the end of the movie when they are in their big 4x4 destroying the camp, they jump off a small cliff. It is a night scene so they have their headlights on. They cut outside the truck as it jumps and both headlights work. They go back inside, then outside as it does a hard landing. You can clearly see one light is now out from the impact. They go to another inside shot, then outside after it lands. Both lights now work.
Continuity mistake: When Tango and Cash escape from prison, they slide down an electric cable. When Stallone is running to the wire, he has nothing in his mouth. In the next scene, when he jumps to the cable, he has a belt or rope in his mouth.
Continuity mistake: In the beginning of movie, when Cash and Tango's sister are on the couch, she is facing one way. In the next shot, she's facing the opposite way.
Revealing mistake: When Tango and Cash are getting attacked down the laundry chute, they are tied up above a water tank with a guy holding an electric wire. Their hands are tied to dry cloth which is then tied to the cable. Cloth has no conductivity so there is no complete circuit when their feet are lowered into the water so they wouldn't be getting shocked. The reason they wouldn't be getting shocked is actually explained later in the movie just before they slide down the electric wire.
Revealing mistake: When Cash stuffs the grenade in the trousers of the guy with the ponytail and throws him down the stairs, you can see that the explosion doesn't come from the grenade but from the hall on the right side of the stairs.
Revealing mistake: When Tango and Cash hold a bad guy upside down off a roof, Tango has his arms straight out in front of him, elbows locked, parallel to the ground. This would require incredible strength. In the next shot he holds the bad guy properly, held close to his own body with his elbows bent - but Tango appears to be exerting no effort in order to lift the guy at the beginning of this new shot. We can also see the outline of a harness system to hold the bad guy up under the black silk shirt of the bad guy.
Continuity mistake: In one scene, Tango sees a man looking in through the screen door, he jumps the man and rips open the screen. In the next scene, the screen is back to normal and covering the man's face.
Continuity mistake: Cash spins out the truck of the bad guy and it stops all forward momentum, but in the next shot it is racing at full speed. The truck then takes out many overhead fluorescent lights. Why has no other vehicle ever hit those lights? Then the truck partially knocks down 7 lights in a row, leaving them hanging vertically. They were damaged enough to knock them off the ceiling - but they are all undamaged enough to still be operating: keep in mind that these are fragile fluorescent lights. But no damage is done to the floodlights on the roof of the truck.
Revealing mistake: When Cash's stuntman jumps out the window after the bad guy, his feet move out in front of him so that he will land on his back (on an airbag) - cut to next shot and his feet are magically underneath him as he lands and rolls. As (Cash) runs around the street corner it is obviously a stuntman. When Cash runs down the narrow alley he is not wearing a bulletproof vest, but in a following scene he takes one off.
Continuity mistake: Tango is in the FBI agent's house and the guy pulls the handle of his car to get away and his car blows up. Tango flies through the air without his necklace. In the next scene, he has it on again. The guy in the air is clearly a stuntman.
Factual error: When Stallone shoots the tanker to show that it's being used to transport cocaine, he's apparently stumbled onto the only drug dealers who don't ship cocaine in bricks. There is no way that the coke would flow out of the bullethole like that.
Continuity mistake: The scene is at Tango's house where he reaches into the refrigerator and pulls out a plate of spaghetti. He drops it on the floor, the shot pulls away, then you see the plate again, only this time it has a fork.
Continuity mistake: Tango and Cash play good cop, bad cop with the bad guy on the roof of the building by taping a grenade to his mouth and intimidate him by threatening to pull the pin. They get the information that they need out of him. Cash says "We scared him so bad, he is standing in a puddle and it's not raining". They then take the grenade, pull the pin and stuff it down his trousers. The next shot is the grenade coming out his trouser leg onto the ground where there is no puddle to be found.