Super Weapon, Average Joe

Some characters aren't really cut out to be dangerous combatants. Maybe they lost the Superpower Lottery, or grew old and weak, or just were never intended to be more than Mooks in the first place. In short, they're too average, or even weak, to truly strike fear in the hearts of the truly powerful heroes and villains.

And then they find a horrendously powerful yet easy-to-use weapon from near the peak of the power curve. Whether it is a wand of hellfire, a BFG or a magical sword, the wielder of the weapon is capable of causing far more severe damage than they were before, making them a force to be reckoned with. After all, who needs skill when one can just pull the trigger and watch the fireworks?

This is different from Amplifier Artifact and Upgrade Artifact in that the weapon doesn't necessarily enhance the wielder - they're still as weak and mortal as before, only wielding an extremely potent weapon. When the powerful weapon is given to a character as a last resort, see Giving the Sword to A Noob.

NOTE: Only list cases where the character's power is clearly attributable to the weapon. If the character is tough regardless of the weapon they use, it's not this trope.

Anime and Manga

 * Yukino Agoria from Fairy Tail is a stellar spirit mage, with two Golden Keys and, but without those three keys, she's completely harmless.

Comic Books

 * In a mid-1980s issue of Justice League of America, an alcoholic drifter's mind accidentally takes control of the super-android Amazo and threatens the world.
 * Even earlier, the Silver Age League tended to encounter ordinary hoodlums who had stumbled upon amazing alien machines that enabled them to take on the entire team. They usually didn't reappear after a single story, typically because the alien devices would be destroyed by the heroes to end the menace.
 * Issue 13 of The Transformers had Megatron getting locked in his alternate mode (as a gun) and being used by a random crook.

Film

 * In RoboCop the criminal gang working for the Big Bad is easily neutralized and arrested by the titular cyborg. When they are later freed from jail, they are given military-grade anti-tank weapons and become a credible threat to the hero.
 * Laserblast. A teenager acquires an alien laser gun. The problem? The medallion he has to wear to use the weapon turns him into an evil alien, and he goes on a rampage.
 * In Captain America: The First Avenger, one of the POW's liberated from the HYDRA facility picks up a tesseract-powered energy weapon dropped by a dead Gas Mask Mooks. Jim Morita asks him, "Do you know how to use that thing?" The POW promptly fires a wild shot, then proceeds to use the gun to begin decimating HYDRA troops.
 * In The Avengers, Agent Phil Coulson, a non-powered special agent, grabs a BFG that had been built from the Destroyer Armor in Thor and uses it against the Big Bad: an Asgardian god of evil!
 * Also in the Marvel Cinematic Universe, Spider-Man: Homecoming shows a variety of small-time crooks getting supergear, courtesy of Adrian Toomes, AKA "The Vulture".

Live Action Television

 * The wielders of the cursed artifacts in Friday the 13th: The Series.

Literature

 * In The Cleric Quintet there is a character named Ghost who is just a normal human with a VERY powerful soul-shifting mirror.
 * In The Icewind Dale Trilogy, there is a very weak wizard that finds a magical artifact that lets him summon demons and stuff, but eventually kills him for his incompetence, choosing to be buried indefinately than to live with him.
 * In The Two Swords by R.A. Salvatore a mundane orc comes to possess Khazid'hea and goes on a killing spree. Up until he runs into Drizzt.
 * Sixth Column's plot revolves around this trope - a group of six ordinary American soldiers and scientists manage to overthrow an Asian occupation by using recently invented horrendously powerful Doomsday Devices that grant them near-omnipotence.

Tabletop Games

 * A published Pathfinder adventure for levels 1-2 features as its final boss a level 2 cleric wielding a +2 flaming greataxe, which a PC could usually not hope to afford until at least 7th level.
 * Early editions of Dungeons & Dragons. More than one Dungeon Master lost control of his game when he let a low level wizard/mage Player Character obtain a powerful magic item such as a fully charged Wand of Lightning or Wand of Fire. The wizard/mage usually went on a killing spree, slaughtering all opponents the party met until the charges ran out.

Video Games

 * Nethack fans know this phenomenon as "The Gnome with the Wand of Death". Gnomes are early game pushover monsters, but like other humanoids and the player, they are smart enough to use wands - including the One-Hit Kill Wand of Death.
 * In Dungeon Crawl, monsters are sometimes generated with branded weapons that can make them extremely dangerous. A mere kobold with a distortion sword can send the player into the Abyss.
 * The aged Altair pulls this off twice in Assassin's Creed: Revelations. First, he assassinates Abbas using his newly-fashioned hidden gun, and later on fends off a Mongol siege using the Apple of Eden.
 * The Max Payne series has only a few types of enemies (mobsters of various ethnicities, MIBs, black ops and this is all) but they differ by the weapon they wield. So even a puny Mafia soldier becomes dangerous if he's equipped with a powerful weapon like a sniper rifle or an M79 grenade launcher.
 * Halo has Grunts. Gas Mask Mooks and eternal Butt Monkey species of the entire series. They turn incredibly deadly when equipped with the Fuel Rod Gun.
 * The mission "Crew Expendable" from Modern Warfare contains one Mook armed with a Desert Eagle. Plus he's in a dark corner of the level and is positioned so that he'll probably come at you from behind.
 * In Super Paper Mario, there's one Koopa Troopa that realizes it can take the invincibility-granting starman powerup for itself. Unfortunately, the powered-up Troopa is still vulnerable to certain attacks, unlike a star-powered Player Character.
 * In Kid Icarus Uprising,

Western Animation

 * An episode of Batman Beyond had The Jokerz get hold of an experimental fighter aircraft. It was powered by an unstable reactor (which is why the pilots had to ditch it), meaning Terry had to get it back from them before it exploded.