Blinded by the Light

In works of fiction, heroes and villains alike will find every advantage to winning a battle, whether it's a personal Duel to the Death or the ultimate Final Battle. One of the simplest and most prevalent is based on a notion that if the enemy can't see you (or anything), they can't hit you: shining a super bright light source directly into the face of your enemies. This will work to varying degrees depending on the work, from completely blinding and incapacitating your foe to causing just a momentary inconvenience.

Depending on the work, the light source could be any number of things. For example, in Fantasy works it's likely some sort of magic had a hand in it, while in Science Fiction it is more likely to find flashbang grenades or devices specifically designed for this sort of thing.

If some characters have been in the dark for a while, this can occur with much weaker lights than normal, while leaving other characters unaffected, since Day Hurts Dark-Adjusted Eyes.

An example of Truth in Television, since the use of flashbang grenades is highly prevalent in modern police forces and armies have been using natural light in various ways to blind and hinder their enemies for centuries.

Compare: A Handful for An Eye, Tap on the Head, Inescapable Net, Stun Guns, Instant Sedation. Has nothing to do with the battle theme for Final Fantasy XIII.

Anime and Manga

 * At the beginning of Saint Seiya's "Asgard Saga," the God Warrior Syd of Mizar Zeta makes a very effective point to Shun about "attacking in the direction of the Sun" by leaping above him and using the bright midday Sun to blind the Andromeda Saint.
 * In Nausicaa of the Valley of the Wind, attacking from above and using the Sun's glare to hide his position from aircraft turrets is Prince Asbel's favored strafing tactic.
 * Madoka Magica: Homura's extensive arsenal includes flashbangs.
 * Fullmetal Alchemist
 * Ling Yao uses a flash grenade while fighting Wrath to blind his one working eye. Too bad about the other one though.
 * Fu also uses a flash grenade to
 * One Piece
 * Parodied during the Skypiea Arc. Zoro found himself in a swords vs. guns battle with a Shandian, who used pistols that were equipped with Flash Dials as to blind the opponent anytime he shot at them. Zoro realized he can combat this with his goggles, but unfortunately, The Goggles Do Nothing since they're not tinted at all.
 * The Flash Dial comes back during Luffy's fight with Usopp, which he uses after making Luffy hesitate with a cough of fake blood.
 * Sky Girls:
 * During the first episode, Ace Pilot Eika got defeated by a new, Sonic Diver-piloting test pilot when her target transformed and attacked from the direction of the sun. Granted, she is using a conventional fighter jet at the time and her opponent is very nimble.
 * In a true show of piloting ability, Eika used the exact same tactic combined with careful maneuvering against a Teen Genius who very nearly beat her through sheer talent later in the series.
 * The characters on Dragonball Z sometimes use this, calling it "Solar Flare".

Comics

 * In X-Wing: The Phantom Affair, a gang of pro-Imperial thugs attacks Rogue Squadron pilot Tycho Celchu. He beats most of them down by himself, but the last one gets the drop on him and is preparing to deliver the final (possibly fatal) blow, when he's slashed through the eyes by a phantom Jedi's lightsaber, causing instant blindness and much pained yelling. It turns out later that the "Jedi" is just a hologram, and given that holograms are actually just light (lasers, to be specific), this trope stands.
 * One issue of The Punisher has him narrate how devastating a single flashbang grenade is to the senses. The next panel shows him dropping three at once through a skylight on some mobsters.
 * Harley Quinn does this to Deadshot in Suicide Squad #7. Harley kills the lights, knowing tha Deadshot will switch to infra-red. As soon as he does so, she sets off a magnesium flare.

Fan Works

 * Princess Celestia blinds Nightmare Moon by empowering the sun's glow in the My Little Pony Friendship Is Magic fanfic Whispers.

Film

 * Lord of the Rings: This happens to the Uruk-hai at the end of the Battle of Helms Deep when the sun rises behind the charging cavalry.
 * Hook: The Lost Boys have one set of weapons that use mirrors to blind the pirates during the Final Battle.
 * Frequently shows up in action movies against bad guys with Night Vision Goggles.
 * Transformers: The Movie: Hot Rod shines his headlights into Galvatron's optics during their battle (in a dark room), and Galvatron's flinch gives Hot Rod a couple free shots at him.
 * In Kick-Ass, Hit Girl uses a gun with a superbright flasher when she attacks in low light. It blinds the bad guys, but allows her to see everything.
 * Enemy at the Gates has Vasili pinned down behind a piece of rubble by a German sniper. His Love Interest uses a mirror shard to reflect sunlight right into the German's scope, making him flinch just long enough for Vasili to take a snap-shot at him and get away.
 * In Game of Death, the enemy played by Kareem Abdul Jabaar has light-sensitive eyes. Bruce Lee gains the advantage by breaking holes in the walls to let the light in.
 * In A Kid in King Arthur's Court, Calvin opens his CD player and shines the laser into a bad guy's eyes.

Literature

 * In Robert E. Howard's Conan the Barbarian story "A Witch Shall Be Born", Salome uses light to blind Tamaris's rescuers.
 * In the first book of The Legend of Drizzt, Drizzt floods the room with light to escape from his family (who are now trying to kill him). Being creatures who live their whole lives in the dark underground, the light is not only blinding, but painful as well.
 * The Black Magician Trilogy: Sonea pulls this off when being harassed by other apprentices at night. She doesn't want to fight back, because she's much more powerful and could hurt or kill them. Instead, she turns off her magical light for a few moments, so their eyes adjust to the darkness, then turns the light Up to Eleven. Her assailants end up temporarily blinded.
 * Tom Clancy uses this in a number of his Jack Ryan books. In addition to the standard flashbangs, Debt of Honor features a high-intensity blinding light weapon, stated to be a nonlethal weapon. It is indeed nonlethal, if horribly effective, when used on a mook. Then it's used on the pilots of enemy aircraft as they're attempting to land their planes.
 * Subverted in James Follett's The Tiptoe Boys (later filmed as Who Dares Wins). The SAS soldiers rescuing their comrade's family can't use flashbangs because it will cause permanent neurological damage to the hero's infant daughter. They settle for
 * In Devon Monk's Allie Beckstrom book Magic to the Bone, Allie uses this on a would-be kidnapper: a two-second flash, too simple and chidish to be expected.
 * In John Gardner's James Bond novels, one of the modifications fitted to Bond's car is a high-intensity halogen flashbulb replacing the bulb that illuminates the number plate. This is used to blind pursuers.

Live Action TV

 * Highlander the Series had a rogue Watcher who killed other immortals in complete darkness with night vision glasses. Duncan got the edge on him by blinding him with light from a match or lighter or something similar.
 * In Spartacus: Blood and Sand, Crixus reflects sunlight with his helmet into Theokoles' eyes, allowing Spartacus to get close enough to kill him. As Theokoles was an albino, his eyes were especially sensitive to light.
 * Done at least twice by Team Westen on Burn Notice, the first time with a homemade flashbang, and the second time with a car's hi-beams.
 * In "Live Fast and Prosper" on Star Trek: Voyager, the Voyager crew comes up against a group of con artists who have been impersonating Janeway, Chakotay and Tuvok. Tuvok eventually comes face-to-face to with the man who is impersonating him and the con remains in-character, commenting that "Logic would indictate that neither of us has the advantage." Tuvok comments "Your logic is flawed," shines a flashlight in his eyes, then stuns him with a phaser.

Tabletop Games

 * Dungeons and Dragons: Features a variety of spells that use light to blind and/or incapicitate an enemy.
 * Mutants and Masterminds sports the Dazzle power which can do this for any sense.
 * In Magic: The Gathering, this is often used by users of White Magic, specially these two.

Video Games

 * Some mechs in Mechwarrior Living Legends mount large spotlights on their shoulders, which can be used to blind players using the nightvision overlay when it's dark.
 * Alan Wake: The game's combat system is based entirely around using light (from flashlights, flares, flashbang grenades, etc.) to damage or render vulnerable the various enemies. Also, some NPCs react to the player shining a light in their face by shielding their eyes.
 * Call of Duty: Most iterations of the series features grenades that can blind your enemies (or yourself if carelessly used).
 * Heroes of Might and Magic: Most iterations of the series have a spell called "Blind" that effectively works this way.
 * Luigis Mansion: Luigi must use his flashlight to shock ghosts so that he may inhale them into his vaccuum.
 * Neverwinter Nights: Well, it is based on Dungeons and Dragons after all...
 * World of Warcraft: PCs and bosses have abilities that can use light to completely incapacitate or at least hinder accuracy. A recurring element with bosses is the need to turn characters so they're facing away from the boss to avoid being blinded by the flash.
 * God of War:
 * Aside from using it as a makeshift flashlight, Kratos can put Helios' severed head to great use by blinding enemies with it. In fact, employing this strategy is how you're supposed to defeat Kronos the Titan.
 * Perseus uses his reflective shield to blind Kratos several times in his boss battle.
 * In Mass Effect 2, flashbang stun grenades are Kasumi's special power that are unlocked once her loyalty mission is completed. With advanced training, Shepard can use these grenades as well. Donovan Hock's mercenary guards and the Shadow Broker's troops also make regular use of flashbangs.
 * This is the basis behind the Pokémon move Flash, which can be used in battle to drop the opponent's accuracy one stage. Of course, that doesn't mean it is used very often, what with several other moves being able to do this with more success, and the relatively low benefit reducing accuracy has in the game.
 * In Final Fantasy VI, Edgar Figaro can wield the Tool "Flash," a camera with a flashbulb as big as he is. It deals unblockable, defense-ignoring non-elemental damage and inflicts the Blind status effect on enemies.
 * Armored Core 4 and 4 Answer gives you the 09-FLICKER Flash Rockets. These literally are flashbang in rocket form and having it set off anywhere near you means that you lose lock-on capability for some time. Very bad against close-range combatants like Anjou/Ange, and especially Shinkai. Getting hit by an Assault Armor in 4A will also produce this effect.
 * Happens briefly early in Fallout 3, when your character leaves his underground vault for the first time.
 * It only happens once in Fallout: New Vegas, when you first properly activate the Helios One facility, you get blinded for just one second.
 * Wizardry: The Blinding Flash spell in the final trilogy. Simple and very effective throughout the early through middle parts of the games.
 * Flashbang grenades are, appropriately enough, a common tool in your arsenal in SWAT 4. Just make sure you're out of the doorway when you use one and that your NPC teammates don't, y'know, just drop it at their fee--GAH! YOU FOOL!
 * Battlefield 3' features the tactical flashlight and laser sight. The latter is a red laser that is primarily used to boost the effectiveness of hip fire, but also causes an annoying red spotlight to cover the targets vision if it is aimed at them. The former, on the other hand, is purely used for blinding foes. By blinding foes, I mean melting the eyes of the person controlling the target to a molten liquid, and setting their hair alight.
 * Weaponized as a secondary function Spark Manbow in Rock Man 4 Minus Infinity. If you hold up when you press the fire button, Mega Man holds up a lightbulb and causes a bright flash of light to cover the screen, which makes enemies stand still for a few seconds.

Web Comics

 * Bob and George: Someone tries to use this against Bob. Alas for him, Bob is wearing sunglasses.
 * The Beast Legion : Brilight uses this particular trick twice in Issue 4 against Dragos ,
 * In Far From Home, pirates use high-intensity flares in missiles so as to take the heroes alive.

Western Animation

 * Used in Trollz when ogres are sensitive to light. Good thing Sapphire's spell misfired earlier and made her feet glow.

Real Life

 * There was a biblical battle that took place and overall the terrain was consistent no matter which direction you would attack from. So the attacker came around dawn from the east so the sun would be at his mens back and in the eyes of the enemy. This is actually a very valid tactic: if you can use it do so.
 * World War One / World War Two: Attacking out of the sun was a popular tactic for both fighters and dive-bombers.
 * During the age while armies still utilized campfires at night, it was not uncommon for those to be used as a means of deception. Merely looking at a light source at night temporarily ruins the eye's low light adjustments, meaning that while looking at such a campfire (or for that matter any other light source at night), it was impossible to actually see the people (if any) that existed around it; only the light source would be visible. Armies got pretty creative with this back in the day, from setting up false camps (the enemy won't know theres no one by the fire until its too late), to lighting a minimal number of fires to hide their number (sometimes going as far as just one big fire; good luck guessing how many people are sharing it), to ordering the camp to make several times its number in flames. A cunning general may even combine the various methods, essentially rendering the enemy's attempts to scout his position at night futile or downright counterproductive. Even in warfare, there are uses for fire other than killing.
 * One of the armored vehicles used in the Normandy landings in World War Two was essentially an outdated tank with the gun replaced with a very high intensity lamp, entirely encased in the turret save for a narrow vertical slit. The turret would pan back and forth, perodically painting the German defenses with blinding light to make it impossible for them to see the troops on the beaches. They also had various filters they could put onto the light while in action, so as to make it harder to determine how far away the vehicle was if you wanted to put its lights out.
 * In World War II, the British "hid" the Suez Canal with an array of spotlights and shifting reflectors intended to dazzle the eyes of bomber pilots. When they tested it by having two British planes fly into the area, they found the effect disoriented the pilots so much that both planes nearly crashed -- just from flashing lights. Best part? This was just one stunt thought up by Jasper Maskelyne,War Magician.

Eventually, a chain of twenty-one searchlights covered the Suez Canal for its entire length. When illuminated, they created a curtain of swirling light over more than a hundred miles of Egyptian sky. In the following months enemy aircraft made a number of attempts to penetrate the curtain, and failed, and the canal remained open to Allied shipping throughout the war.
 * The LED Incapacitator, a rather recent non-lethal weapon which works by creating a bright pulsing light with continously changing colours to dazzle and disorient an opponent when violence is not permitted. Again a very valid self defense tactic, very bright hand held torches might be expensive but stun\flash grenades operate on the same principle, making them worth every penny.
 * A more mundane example: pilots who fly at night have to avoid any bright lights for upwards of 20 or 30 minutes before a flight in order to maintain their night vision. Their cockpit lights are run at the lowest setting that lets them see their instruments, because any bright light will force them to start all over again trying to readjust to the darkness of night. As a result, airports will often actually be much more dimly lit than some folks might expect, as the last thing they want to do is to blind a pilot who is trying to take off or land.
 * Similar to the above, go out some night to visit a group of stargazers out doing their thing, and you will quickly learn that they do not like it when folks use any bright or white light near where they are stargazing. Stars are bright, but they are not that bright compared to closer light sources on Earth. The use of red-filtered light is common as it does not have the same negative effect on human night vision.