Want to show how good and just your hero is? Then just use this counterpart to Casting a Shadow: Light! This frequently involves healing and divine powers, although this can mean literal light as well. This may overlap with Holy Hand Grenade if the powers in question are used to attack. Like most other types of elemental manipulation, the laws of physics give way to Rule Of Cool.
Light has many similarities to fire, producing both illumination and heat. Thematically, however, fire is often presented as a primal or destructive force, whereas light is a protective force that literally illuminates the darkness. In some cases, light and fire overlap and sometimes intersects with electricity as well. All three of these powers may also possess qualities of purification or total destruction, depending on the work in question. See also The Power of the Sun, as, in fiction, a solar power is occasionally a mixture of the powers of fire and light.
The Hero is likely to use this, and if so, is likely to be a saint. The hero is likely to learn this from the Big Good or the Obi Wan, who will be the master of this. Alternately, a work may instead use Light Is Not Good, in which case, this may be used by the villain. In that case, similar to how The Sacred Darkness illustrates a way to portray Casting a Shadow in a pure and holy fashion, a villanous or "corrupt" form of light may involve such lovely things as light so bright that it burns out the victim's eyes, causes his flesh to be brutally melted off, etc.
A Sub Trope of Elemental Powers. Usually trumpsdarkness, though the reverse is also possible. Or both, even. For double the fun, see Yin Yang Bomb. See also The Power of the Sun, which may or may not be related to this, depending on the setting.
This trope is Light purely acting as its own element. A Super Trope to Holy Hand Grenade, when Light attacks are fueled by good.
D.N.Angel features Dark's opposite who, in his very first appearance, uses what looks to be light-based magic. While having white wings. And glowing blond hair. Yet he is, by no definition of the word, good.
Leo, the Stellar Spirit of Fairy Tail, has this as his main power. Makes sense, since the Zodiac Leo is linked with the Sun.
Jellal and his Heavenly Magic.
Sting, the White Dragon Slayer can use this as his power.
Makarov, Laxus and Mavis Are all capable of casting the light based Fairy Tail exclusive spells.
The closest to genuine light powers exhibited in Fullmetal Alchemist (not counting Father's acquired solar powers when he literally ate God) are the ones shown by Solf J. Kimblee, the psychopathic, Ax Crazy Red Lotus Alchemist. His powers are explosions of intense, white light generated by the energy of combining the symbols he has tatooed on his hands, one standing for the Sun, fire, and gold and another standing for the Moon, water, and silver. In practice, it's more like throwing around magnesium on fire than firing lasers, but works just as lethally.
Sunny Milk, from the Touhou official manga Eastern and Little Nature Deity, has the ability to control the refraction of light. Of course, being a fairy, this is used mostly as a cloaking device in her trio's pranks.
In Sailor Moon, Minako Aino/Sailor Venus primarily uses light-based attacks. Her first attack that she uses is Crescent Beam, which is a beam of light.
Yu Yu Hakusho also has Divine Energy, whose primary signature is the golden glow that surrounds a user while channeling it.
Angemon and Angewomon of Digimon Adventure. Angemon's "Hand of Fate" is his hand glowing with divine light which he proceeds to punch at the enemy. Angewomon has "Heaven's Charm" which works very much the same way.
The Ray from the DC Comics universe can, according to The Other Wiki, absorb, store, and process light and use the energy to fly and create bursts of light. The Terrills were also capable of manipulating external light, allowing them to create illusions and even solid light constructs, and to render themselves invisible.
Dr. Light from the DC Comics can manipulate light, originally thanks to a suit he stole, but afterwards, said ability became natural to his body. Mind you, while there is a good Dr.Light (a japanese female scientist) in the DC Comics, the original one was the ultimate form of Light Is Not Good, afterwards turning into a rapist.
Although Ms. Marvel was not able to do it at first, after she was experimented on by the Brood, she became capable of absorbing energy and projecting it, as well. Nowadays, being able to use photon blasts is one of Carol's signature powers. Her Spear Counterpart, the original Captain Marvel, was always capable of doing it.
The second Captain Marvel, Monica Rambeau, generates and turns into light as her main power.
Northstar and his twin, Aurora, from X-Men and Alpha Flight are capable of flight and superspeed, and originally, if they came into contact with each other, they could generate bursts of light. Since then, their powers have been revamped so that the two are capable of doing so individually.
Also, Dazzler of the X-Men is able to convert sound into light for various purposes, including Frickin' Laser Beams, holographic images, and blinding flashes of light.
Tandy Bowen (Dagger of Cloak and Dagger) is capable of creating daggers made of light for offensive purposes and can even purge addictions from people. Dagger also uses these light daggers to satiate her partner Cloak's hunger for light when he uses his Teleport Cloak.
Runaways gives us the light-powered Majesdanians, who look exactly like humans when powered-down (or when they're wearing a certain type of metal), but look like rainbows in their natural state.
The whole Green Lantern franchise is more or less based on this, with various factions being able to manipulate light of different colours of the emotional spectrum.
The Magic Knight, dwarven, noble protagonist in Dragon Age The Crown Of Thorns. While he is a Guile Hero, he fulfills the necessary good/heroic requisites. The fact that he can cast a white battle aura which can get bright enough to illuminate corridors perfectly is just a side effect of the fact that he can never really control the tear in the Veil he has anchored in his body, with said light being just extra magical power that automatically takes the shape of the Spirit of Honor, the DN's not-spirit-advisor, when he uses magic to perform extra-badass feats.
Thanks to a light spell he learned early on, Paul in With Strings Attached can make part or all of his body glow via his hair, teeth, and nails. This proves to be extremely useful and is the power he uses the most after his invulnerability. Once, in a rage, he generated some kind of laser blast from his fingernails. When at high strength, he can pump extra power into the light, to the point where he literally explodes.
The Lord of the Rings - this seems to be Gandalf's main attribute note more than in the books. He can conjure a shield of light, enhance the sunrise to disrupt the Uruk-hai, and use white light to drive away the Nazgűl.
Stardust's anthropomorphic star can shine. Quite useful when lit up to full power in the witch's abode.
Kendra, from Fablehaven, glows - blindingly - to most mythical creatures, after becoming Fairykind in the third book. She also takes possession of a talisman of light, which casts a large umbrella of light around her and her friends as they go to do what they do best - fight evil.
Sam from the Gone series seems to have the power of light. When not using it offensively, he can use it to provide light. Bette was also able to make her hands glow, until Orc killed her.
Harry Potter gives us the Patronus Charm. Used to great effect in the movies. As well as the Lumos charm and subsequent derivations.
The film version of the first book has Hermione casting a spell to replicate sunlight to drive off the Devil's Snare.
In Teresa Frohock's Miserere An Autumn Tale, only good guys can cast the light spell. It is not very powerful, but very useful for establishing yourself.
In the second arc of The Saga Of The Noble Dead, the sage Wynn wields a magical staff that generates sunlight, which is capable of destroying the undead.
Zeddicus from The Sword Of Truth makes light "webs" (spells) these are epically destructive often manifesting in the form of large explosions.
Gandalf in The Lord of the Rings claims at the bridge in Moria to be "servant of the Secret Fire, wielder of the Flame of Anor." Anyone who's read the Silmarillion knows he's essentially saying "I'm an angel of God. Mess with me, and I'll drop sunfire on your Balrog butt."
Alice in The Magicians specializes in phosphoromancy, a magical discipline focused around the manipulation of light. You know how kids will burn ants with a magnifying glass? She creates a magical "lens" a mile wide to focus sunlight into Frickin' Laser Beams.
Pretty much everyone according to Gnosticism; humans are shards of light trapped in human flesh that can reach their powers via enlightment, the Aeons live in greater realms of light, and even the Yaldabaoth and his servants, in spite of traditional metaphors as "darkness", appearently are still capable of light powers, with the Archons Iao and Adonaios being associated with the Sun and Jupiter and the archon Horaios having a name that means "light".
Most good Clerics and Paladins in Dungeons & Dragons live and breathe this trope, and the game also has spells such as Searing Light, Sunbeam, and Sunburst, as well as the various Prismatic spells.
Exalted - the Solar Exalted, unsurprisingly, have a fair bit of light imagery - they glow like the sun when they exert themselves and have plenty of other light-based tricks. Their Hellish mirrors, the Green Sun princes, have access to a few effects based on the Green Sun of Hell.
In Nomine has the Celestial Song of Light, which creates a supernatural laser beam.
Many (or possibly all, depending on how loosely you define this trope) White spells fall into this.
Red also has a few spells that involve using light beams, such as the iconic Cleansing Beam. Like most Red spells, they are extremely agressive in nature, their purpose being to burn the enemies. White, of course, still has similar spells, but they usually erase the victim completly instead of simply burning it alive.
Puncture Blast in particular is interesting because flavourwise it seems to illustrate the "corrupted light" concept mentioned previously (the mechanic "wither" is basically flavoured as, well, withering).
Mutants & Masterminds, being comic books incarnate, has Light Control as a power, and it has plenty of sub-powers available.
The Light Wizards of Warhammer Fantasy use, live by, and ARE this trope. Their Light-related magic has many purposes: Daemon Fighting, Healing of the Soul and Body, and Illumination of the Mind and Darkness.
Light is one Attribute of monster in the Yu Gi Oh card game, and most monsters of the Attribute seem benign (most Fairy-Type Monsters are Light, for example)... But not all of them. Light Is Not Good occasionally applies with a few archetypes of monsters, such as the Fiend-Type Fableds and the Lovecraftian-looking Arcana Force monsters.
The Exalted, in particular those of the Celestial variety, all begin to glow when they start throwing their powers around. While they do have plenty of benign powers, they were created to fight the creators of the universe...
More literally, there are two Adamant Circle spells; Cleansing Solar Flames, which burns every "creature of darkness" within several miles, and Light of Solar Cleansing, which restores Shadowlands to normality by severing their connection to the Underworld.
The Light element in Bionicle, including Takanuva, Toa Of Light.
In the Kingdom Hearts series, it's common for the main heroes (Sora, Roxas, Xion, King Mickey, Aqua, and Ven) to have a tendency towards Light based attacks as their signature moves. The three exceptions are Casting a Shadow and Playing with Fire instead.
In League Of Legends, Lux (who actually says this trope) and Leona both use light - Leona uses sunlight specifically, while Lux uses light in general. Both have an emphasis on protecting their allies and hindering enemies, although they do it in different ways.
Light is one of the elements from The Legend Of Dragoon. The users are Shana and Miranda. Furthermore, only a tiny number of monsters have this element.
Mega Man X: Optic Sunflower from X8, who attacks with lots of laser-based moves, and Shining Firefly/Izzy Glow from X5, who attacks with a huge laser. To a lesser extent are Sting Chameleon from X and Neon Tiger from X3, who use optical lasers and ray sparks/laser claws respectively.
In Okami Amaterasu can make the sun appear in the sky and change night to day. She is, after all, the sun goddess. She is also weakened during the eclipse at the end of the game.
In Onimusha 3 and 4, the Light element appears. In the third, it's linked to the Tenso swords and consist in an extremely fast, multiple slashing attack. In the sequel, Light magic releases a stunning flash of light followed by a Beam Spam attack.
Pokémon, surprisingly, does not have a specific "light" typing in its wide-ranging Elemental Rock-Paper-Scissors System. However, it does have a few moves that are based around weaponizing light:
The Normal-type Flash is used to blind the opponent/light up dark passages in the field.
Lots of Electric-type moves also have lots of flashing effects. Even Thunder, which is actually more lightning.
Solarbeam, a Grass-type move. And it's more efficient with Sunny Day, a Fire-type move.
One character in each Shadow Hearts game wields the Light-element. In the first game, it's the love interest; in the second game, it's the main character's cousin; and in the third game...it's a Highly VisibleMcNinja.
The main villain of Tales Of Symphonia casts light magic and has a strong resistance to your own light spells, as do several of his associates and minions. Collete and Raine's offensive spells are also light-based.
Cheria Barnes and Richard in Tales Of Graces. While the game lacks the standard elemental classifications for magic, they utilize spells that are of the light element in the other games, such as Holy Lance and Indignation. Also, Sophie has a definite light theme to her attacks, with the word "photonic" coming up a lot in her arte descriptions.
Lyla in Visions & Voices. The Wanderer can switch between light and dark skills using a skill called "Reverse Polarity", as well.
Wisp magic in the World Of Mana series is light-elemental. It also includes healing.
World Of Warcraft has both paladins and priests, who can use Holy spells to both heal allies and damage opponents. Discipline priests can actually heal people by smiting their enemies. Officially, this isn't always drawn from light - for example, Tauren paladins draw their power from the sun, while night elf priests draw it from the moon. Visually, though, it always looks like light, and several races do draw it from the Holy Light.
From the Global Guardians PBEM Universe, Neon, Strobe, Spectrum, Photon, Allustria, Fireworks, Peter Pan, Solar, Sunspot, Eclipse (who can also manipulate darkness), Dagger, Tinkerbell, Independence, Blue, Rave, Rainbow, Senhora Luz Solar, North Star, Shining Dawn, Brightstar, Eclat ("Burst" in French), Iris, Ushas, Moonshadow (who, like Eclipse, can also manipulate darkness), Tecza ("Rainbow" in Polish), Prezma ("Prism" in Russian), Ion, and Radian can all generate, control, and manipulate light in various ways.
In Today I Die, the protagonist uses light to progress through the story.
Neopets' elemental system includes light - light-based weapons, Light faeries, etc.
Beacon can blast sunlight from his hands. He's on a team that hunt creatures of the night.
Also, Prism, who may be known more for his healing powers, but who can also fire energy blasts and is definitely solar-powered. Well, he is the avatar of Apollo...
Almost all unicorn characters in My Little Pony: Friendship Is Magic have demonstrated the capacity of generating light with their horns at some point. Special points go to Twilight Sparkle (when her friends embody the Elements of Harmony). The god-princesses (known in fanon as alicorns) Celestia and Luna command the Sun and the Moon respectively, so they most likely have this power as well, potentially considerably magnified. Celestia actually gets to demonstrate it in the Season 2 finale. Unfortunately, the villain she was trying to blast was boosted up on stolen love power and won the Beam-O-War duel.
Teen Titans - Doctor Light. Actually manages to be more powerful than the Teen Titans themselves during his debut episode, except for Raven, who traumatizes him to the point that, by merely showing up, she defeats him instantly.
Dr. Light: (weakly) I'd like to go to jail now, please...
And it's even worse for the poor sap in his last appearance in the series, when he decides to commit a crime in broad daylight while every Teen Titan in existence is in Jump City, having just defeated the Brotherhood of Evil. It's just too bad we never find out how that turns out.
Stella from Winx Club gets her powers from the Sun and the Moon, and her attacks consist of casting beams of light.