Not a myth--the Teflon "thing" came about because a company in France was going to import a line of handgun ammo called "Arcane." The primary features of those were that the rounds were not cats, but lathe-turned (to a 60-70º cone) from a brass alloy barstock. Since these rounds would have zippy velocities, the engineers came up with coating them in teflon-like coating to go a little easier on the rifling of the pistols that shot them.
Like many small operations with insufficient capital and under-sophisticated business plans, they folded before really opening. But, the ninnyhammers were convinced that the ammo was as common as crackerjacks. Yet, everyplace the press went to get a box, they were thwarted. Except that was right about the time that the Black Talon was being marketed. This was a match made in media heaven. For comparison, Hydra-Shoks were just coming out, too (and with some built to LE spec rounds, not LE only restricted); yet these were not evil CKB that went through vests like they were rice paper.
Myth--all semi-auto copies of FA arms only need 30, 40 seconds with a screwdriver (maybe a file) to be remade as FA again.
Myth--all dropped arms go off; FA arms go off until the scene gets boring.
Myth--all FA are heavy and awkward and knock down whatever hapless sap picks one up--unless they are the righteous Hero, in which case they need not aim at all, and will be crack shots from the hip (which is made easy, as their weapon will never run out of ammo or the barrel get too hot, or the like).
Myth--evil, twisted, snipe spends his entire life to hone his shooting skills (and shoots everything to identical accuracy, from a PPK to a .338 to a 14.7). His scope has the zoom capacity of an 800mm telephoto lens.
But, a housewife can be taught to shoot with one or two-dozen rounds in a single session. After which she'll shoot 1/8 or 1/4MOA, and will be able to easily peg the bad gut in an an arm or leg, so that the PD will take the BG straight to prison.
Myth--LEO regularly shoot people, like once every other shift; this is why every LEO is a crack shot, and expert in all firearms. (There's a bon mot out there that more people were shot in a single Miami Vice episode, than we shot in Miami during a season of the series.)