Scarecrow Solution

When the heroes cannot directly challenge the villain or his mooks they disguise themselves as monsters or build something that's basically a tank with a threatening exterior. Usually relies on intimidation more than any actual weapons. When villains resort to this tactic, it's a Scooby Doo Hoax.

Comic Books

 * The Life and Times of Scrooge McDuck from Don Rosa - the first chapter when Scrooge scares the Whiskerville away by making a fake ghost.
 * A repeatedly used plot element in lesser Donald Duck comics - a variant involves making some idol worshiped by primitive people appear to speak and tell them to stop roasting the heroes or whatever.
 * One Sam and Max story ("Monkeys Violating the Heavenly Temple") has Max about to be used as a sacrifice for a volcano cult. Sam tries this trope, covering himself in mud to ape the volcano god the cult worships. Not only are the cultists not fooled, they beat the stuffing out of Sam.

Film--Animated

 * An American Tail, the Giant Mouse of Minsk.
 * A Bugs Life, the fake bird.

Film--Live Action

 * "The Dread Pirate Roberts" rig that Fezzik wore in The Princess Bride.
 * The 1971 film, The Johnstown Monster.
 * In Star Wars, Obi-Wan first appears by scaring away some Sand People who were about to kill Luke. He does this by dressing up in his old Jedi robes and making some weird-sounding monster noises, causing them to flee in terror. According to the associated materials, the sound he's making is that of the Krayt Dragon.

Literature

 * Kehaar in Watership Down, albeit only halfway intentionally - great coincidental timing on his, Bigwig's, and the weather's part make it appear to the Efrafans that the bird was summoned out of lightning by Bigwig.
 * The original short story The Legend of Sleepy Hollow is a very early example of this one, especially if you subscribe to the interpretation that Ichabod Crane is a meddling jerk rather than a protagonist.
 * Another early example features in Edgar Allan Poe's The Narrative Of Arthur Gordon Pym, when the protagonist dresses up as a dead sailor's ghost to scare mutineers into abandoning ship.
 * Used in the Doctor Syn novels. Of course, Your Mileage May Vary as to whether you consider Syn and his crew to be heroes.

Live Action TV

 * In an episode of Rocky Jones Space Ranger, a pair of kids use a Bedsheet Ghost to scare away a claim jumper.

Newspaper Comics

 * Modesty Blaise fakes an alien visitation in "The Moonman" arc.

Western Animation
""That's just a flashlight. Kill them!""
 * In Scooby Doo, though it's often the villain who does this to scare away the Distressed Damsel from a Real Estate claim, etc., the heroes often use this technique as well.
 * Gabe/Toxic Terror from What's New Scooby Doo is good one. In fact, the next to final scene has the Gabe, Shaggy, Scooby-Doo, and the camp kid disguise them as Toxic Terror sending Clyde packing.
 * Velma Dinkley, the brains of Mystery Inc. itself, did this in "Scooby-Doo: Where's My Mummy?"
 * Amy Cavenaugh/Amy The Siren from Scooby Doo Mystery Inc is another good one -- especially since she got Velma hooked.
 * The Avatar: The Last Airbender episode "The Painted Lady"
 * The Venture Brothers episode "Escape To The House of Mummies Part II". Dr. Venture, sitting on Brock's shoulders and dressed in a green blanket waves a flashlight at cultists to save Hank and Dean. It doesn't work: