How easy it is to twist someones neck to kill them.

Defibrillators. They don't start a heart that is stopped. They stop arrhytmias and give the body a chance to return to a normal rhythm.

One I read about once.

Bonking people over the head to knock them out.

If you manage to hit them hard enough to actually put them out like that, they are likely bleeding internally and going to die without immidiate hospital care. Maybe even die anyway.

Gear changes in cars. Any car racing or high speed chase these cars are always accelerating and changing through endless gears despite being on a long straight.

Except Ronin, Ronin does it well since the chase is in the city and they're always slowing to avoid objects turn down alleyways etc so going through the gears over and over actually makes sense!

Coffee cups and suitcases.

A whack to the head just puts people to sleep for a few minutes and then they carry on like normal.

Cars explode after an accident.

Passwords can be guessed.

Up and Down exists in outer space.

People getting shot or killed. In reality, they don’t die instantly. They will act more surprised, then the panic sets in as they realise what happened and the pain sets in. They will cry for help as they slowly bleed out. It will take minutes. But that doesn’t look good on the screen. Some movies did parody this.

The relaxed position of mammalian eyelids leaves them open. Muscles must contract for the eyes to be shut. Dead creatures cannot contract their muscles so their eyes remain open after they die.

You cannot shut their eyes for them by closing their eyes with your hand. Morticians place contacts in cadaver's eyes while preparing the body for a wake. Those contacts grip the inside of the eyelids so that they remain closed.

This is why some cultures have funerary traditions in which objects are placed over the eyes.

TL;DR: you and your loved ones won't close their eyes when they die.

Loudness of gunshots. Every action hero would be deaf.

Archers being told to "hold". Nobody's holding a +100lbs warbow.

Sprinklers. In the vast majority of cases they react to heat - not smoke. They only go off individually rather than all at once and the water inside the pipes is black ink-like rust water sludge, not clear tap water.

Also another plumbing related: you don't need a huge wrench under the sink and drains are not pressurized so there's no water spraying anywhere when you mess with the p-trap.

How long things take.

People drinking in situations where nobody would be drinking.

And, obviously, running faster than explosions.

Sex and relationships in action movies.

The whole "hot chick gets horny for the hero after a traumatizing couple of hours" thing gives a pretty messed up view of relationship building.

Any time a car or other vehicle is involved in an accident, it erupts in a massive explosion or fireball. If every car did that IRL, the fire department would never be out of a job knowing how they hand out licenses like candy.

Telephone etiquette. They just start yapping and then hang up without saying goodbye.

Hacking.
tap tap tap I'm in.
Honourable mention is NCIS Dual keyboard
https://www.youtube.com/watch?v=u8qgehH3kEQ

Most dishonest about? Hard to say, since movies are dishonest about virtually everything. (As escapism, that's what we want.) But a big one that comes to mind is proceedings in courts of law.

In real life, a court case is excruciatingly procedural, spread out over months of correspondence and brief hearings, and the vast majority of them never go to trial. And for the few that do go to trial, there are never any intense, witness-stand confrontations, or inspiring speechifying by the plaintiff or defendant. No attorneys shouting, "OBJECTION!", across the room.

I know of two friends of a friend, one of whom signed a reverse mortgage on his house with some scammers who promised that he could live the rest of his life there, but then who turned around and filed to evict him. Clearly influenced by dramatic courtroom scenes in TV and movies, he seemed to think that "court" meant that he would be able to show up and give the judge a moving soliloquy about being a righteous, disabled veteran, and prevail. The judge did his level best to help the guy out by almost insisting on appointing a guardian ad litem (free attorney!), but he refused. (Sadly, he died before it went to trial, and the scammers kept the house.)

The other one got sued by a credit card company over a charge that was obviously bogus (i.e. from a swimming pool contractor in eastern Europe, which is just who you'd call in the midwestern U.S.), but they had the same mental script: Show up in the courtroom and speechify to the judge. They didn't even respond to the summons and complaint, and the company won by default judgement.

It's maddening.

I think familial relationships are often romanticized in movies. I always see siblings act like they are best friends with each other and in my reality my brother and I are just two people. We like each other but I wouldn’t say he’s my best friend and I don’t think he would say it either.

Nobody has that much time in the morning, or they go to bed at 8PM.

I want to see celebrities walking around sweaty in a hot day. Show us the sweat takes!

Bad cell phone reception is also depicted wrong. But I’m not an expert.

Smashing your phone does not reliably disable it. Odds are the data is completely recoverable, and the device may not have even powered down.

Also ghosts. As far as we know ghosts are not real. Yet there’s an entire genre of movies about ghosts with varying rules.

The amount of trauma the human body can absorb is a bathtub curve based on your morality.

NYC should only ever be depicted with giant piles of trash everywhere.

Pulling people out of a burning building. In reality the smoke and fire is so bad, you ain’t seeing shit, not like the clear visibility like they show in the movies. And I spoke to a firefighter who’d been doing it for 35 years. The guy was teaching fire safety at my workplace. He said he responded to thousands of burning buildings and the number of times anyone’s been saved out of a burning building? Exactly zero. That always stuck with me.