I think it was in the first Timothy Dalton Bond movie where he is driving a big-rig. He throws it into a higher gear and stomps on the gas and the semi truck popped a wheelie! Then, of course, the old classic “huh?” scene in oh so many films. Someone (usually the villain) is blown up or shot dozens of times and is blown out of the window of (airplane/building’s 85th floor) and screams the whole way down. There could even have been a scene a few seconds back showing the bad guy being shot through the head, but when he falls he will be screaming. WTF?
How about every single sceen in “Executive Decison"?”
I started laughing about halfway through the movie and didn’t stop until we left the theater.
All in all my brother and I counted about 40 totally impossible scenes starting with a F117 mating with a 747.
How about when Willis and his buddies were on that damn[list][list][list][list]ASTERIOD?
…:p…
[list][list][]TOM & JERRY[]ROAD RUNNER[*]WIZARD OF OZ[list]
As long as the water isn’t full of crap and you have normal vision, you can see underwater.
However, in Lethal Weapon 2, Mel Gibson is tied and tossed into L.A. Harbor at night. As he sinks to the bottom, he sees, in very clear light, the body of Patsy Kensit.
This seems highly improbable as it was dark outside and the water around L.A. Harbor is going to have a lot of crap in it that would cloud your vision.
Maybe not an actual movie stunt, but still pretty stupid.
In The Gauntlet, Clint Eastwood takes his babe, Sondra Lockhart to a destination (courthouse, I think. He’s a down-on-his-luck cop™, she’s the prostitute-witness™. Everyone’s gunning for them. They get everyone else off the bus, and fortify it with steel plates salvaged from somewhere, then proceed to drive right into the trap, which consisted of a) nearly every BadGuy™, Hell’s Angel, Gestapo – all right, accord to IMDB, it’s “hundreds of police armed with high-powered weaponry.”
Of course, they make it, but not before we get to see the snot shot out of a bus in a raging gun battle that’s as stupid as it is boring.
If I recall correctly the bus in ‘Speed’ was driving towards a section in the freeway that had not yet been built. It looked a bit like this
->…<gap>…______
|_|
sorry, it turns all multiple spaces into only 1, so ignore the dots.
Somehow instead of making a nice parabolic arc down to the ground it kind of popped up and over the gap. Right? There wsa nothing for them to jump off of, right?
Now even the Dukes of Hazard got that right! A series which doubtlessly had 1000s of “… stunts that seem impossible …”
The Mummy Returns . . . one of the few things I came out of that movie wanting was the bulletproof seat cushion.
A.I. . . . no way in hell in real life can a robot survive eating spinach . . . 
In the first Mission: Impossible, a train is pursued into the channel tunnel by a helicopter. There’s some other impossible stuff involving a train in the other direction and the helicopter leaning forward to menace Ethan Hunt with its blades, but forget about all that: just the helicopter flying through the tunnel part is impossible.
I guess that’s why they call it Mission: Impossible, mmm? Six impossible stunts before the closing credits?
A semitruck cannot do wheelies! They probably can’t be tilted on one side in order to avoid a missile, either.