Most of these are literally based on movies, as I read somewhere. Automatic knives were common accessory of a villain in the movies of the period. Movie silencers allow you to shoot in a library undetected. Others are likely a misclassified "the shoulder thing that goes up" (from Predator?)

Also, suppressors. They don’t make a gunshot silent. They make it so you won’t instantly lose your hearing without protection.

> while flash hiders just make it difficult for authorities to spot the location of a shooter.

Flash hiders vent gas to the sides/down instead of straight out so that the shooter isn't blinded as much while firing at night. It does virtually nothing to hide a flash from the person you're shooting at. I get that the articles you've googled say that it hides the flash, but that doesn't make sense logically. It should make the flash a similar size except down/to the sides instead of a cone centered on the muzzle. The gases/gunpowder have to go somewhere.

Flash hiders make shooting at night less terrible.

> Muzzle breaks actually increase the noise level of a firearm, making more detectable than a stock barrel.

Muzzle breaks increase perceived noise for the shooter because the gas is vented towards the shooter and towards the sides. It is not a sound amplifier. It likely slightly decreases the noise in the direction of the muzzle because some of the pressure waves will go sideways/backwards instead of forward.

Muzzle breaks make shooting more pleasant with high powered rifles.

Flash hiders don't actually make gunshots harder to spot, the change the direction of the flash away from the shooter line of sight allowing the gun to be used in low light conditions without blinding oneself, and in modern days allow you to use nightvision devices. Muzzle breaks don't make a gun louder, the make it louder at the muzzle which is why some ranges don't like them. Muzzle breaks don't reduce recoil they reduce muzzle rise which is only really useful for follow up shots.

Flash hiders don’t hide a flash. They’re used to protect the shooter’s eyes from the flash affecting their (night) vision.

Might want to ask yourself where you learned that, then discount that source as a valid source of information in the future.

Video games is where I “learned” it. Outfit a gun in, say, Call of Duty or Rainbow Six. Highlight whatever the particular game calls a “flash suppressor”. I’ll bet it says something like “hides your location from other players when fired”, or something like that.

Which of course is not what a flash suppressor does at all.