Power Tattoo

One of the many components of a Power Makeover, the Power Tattoo is a distinguishing mark that shows a character has a certain set of powers. It may only appear when the time is right, or it may be visible at all times, but it frequently tends to glow. Expect it to be placed somewhere on the body that reflects its usage. The more benign version of Mark of the Beast.

Compare Marked Change, where the marks generally cover more of the body, but only when someone has powered up. See also Volcanic Veins, which similarly glow. A person covered in these is a Human Notepad.

Anime and Manga

 * The Sekirei crests, located on the upper back, in Sekirei
 * The mark of the Battling God from Ranma ½
 * Scar from Fullmetal Alchemist. In the first anime, his brother eventually upgraded to Human Notepad.
 * Hell, most alchemists who are dependent upon circles have them tattooed on their hands/arms for convenience. Scar's just happens to be a little more multi-purpose.
 * And those Homunculus', too.
 * The HiME marks in Mai-HiME.
 * Lena Sayers in Mai-Otome has one as well.
 * All chosen warriors in Fushigi Yugi
 * Hiei from Yu Yu Hakusho.
 * Sailor Moon. The Sailor Senshi have planetary marks appear on their foreheads when the plot deems it important.
 * The Signers, and their antithesis, in Yu-Gi-Oh! 5D's
 * And in Yu-Gi-Oh!, the Eye of Anubis fulfills this trope. Sometimes mistaken for The Eye of Wdjat, which is the symbol on Yugi's Puzzle, it can appear on the foreheads of bearers of the items when they use shadow magic. Glowing gold. It has also turned up on the Steves those under the power of Marik through the Millennium Rod.
 * Would the Orichalcos symbol also count? It does turn up, glowing, on people under its influence like the Eye of Anubis.
 * The Geass mark from Code Geass. Geass users have it on their eyes, whereas those who can grant Geass powers have them elsewhere, typically the forehead.
 * The Tokyo Mew Mew girls have marks on their bodies, indicating that they have been infused with Red Data Animals' DNA.
 * In Saint Seiya, the Bronze Saint, Dragon Shiryu has the likeness of a Chinese long tattooed on his back. It's barely visible most of the time, but reappears as his Cosmo ignites. Unfortunately for him, it also reveals his weakness: the raised claw of the dragon matches the location of his heart, pointing out a fatal flaw in his attack style (he lowers his defense when punching.) Also, when he's close to death, the tattoo vanishes almost completely.
 * Inverted in Kekkaishi: Gen and other part-Ayakashis employed by the Urukai usually have a tattoo that limits their abilities through pain.
 * Tengen Toppa Gurren Lagann and its Spiral Power: the users have generally spiral-shaped pupils. And Lordgenome has spiral body hair.
 * G Gundam. Symbols of the Shuffle Alliance.
 * +Anima markings in Plus Anima, though they're actually scars.
 * Orochimaru's Curse Marks in Naruto, although they turn into Marked Changes when activated.
 * Kyuubi's seal may also count.
 * In King of Thorn, Marco Owen is a Tattooed Crook to begin with, but one in particular marks his upgrade from Badass Normal to Badass Abnormal:.
 * In D Gray Man, Kanda has that huge tattoo over his chest. Or at least the left side of it. It's related to his Healing Factor.
 * Magical Record Lyrical Nanoha Force has the Huckebein, all of whom possess a tattoo on their body to identify their Eclipse infection. Cypha, for example, has one on the left side of her neck. As Tohma shows, these turn into Marked Change when the Eclipse goes out of control.
 * Negi from Mahou Sensei Negima gets these when he initially activates his Magia Erebea
 * Brain from Fairy Tail has these and act as a Power Limiter sort of.
 * After being electrocuted by god, Olgrius is covered in markings in Wild Wind. These pass on to his descendents which mark them as masters of manbeasts. Mikhail's are natural but Syon's are actually genetically engineered.
 * In Tokko people with phantoms inside them develop tribal-looking tattoos when they first awaken their powers.
 * Ai from Dragon Crisis has red markings on her right shoulder caused by the Lost Precious inside her body.
 * Ai from Dragon Crisis has red markings on her right shoulder caused by the Lost Precious inside her body.

Comics

 * The various manifestations of the Sigil in Cross Gen Comics.
 * Green Lantern villain the Tattooed Man (both of them) takes it a step further. His power is making his tattoos spring off his body and come to life.
 * Same goes for Tattoo, his Distaff Counterpart from the short-lived Aztek series.
 * This becomes vital in the Final Crisis mini-series when a specific design placed on the face thwarts alien brainwashing efforts.
 * The Starbrand from Marvel's The New Universe- basically a Cosmic Cube in tattoo form.
 * Warren Ellis's Alternate Continuity, newuniversal, takes it a step further and has four "power glyphs": the Starbrand glyph as above, the Justice glyph (which lets the bearer Detect Evil and generate Laser Blades), the Nightmask glyph (which gives the bearer powerful telepathic abilities) and the Cipher glyph (which gives the bearer the ability to create advanced technology) equating to the four heroes of the original New Universe (Star Brand, Justice, Nightmask, and Spitfire).
 * The new character Ink in the X-Men comics has a different power for each tattoo he has.
 * Kinetix, in The Legion of Super Heroes, when she got her powers restored by the White Witch. In this case, the tattoo was the least unusual part of her resulting appearance, which included white skin, pointed ears, and a tail.
 * In the wonderful but unappreciated DC comic Son of Vulcan, the main character Mikey gets the previous Vulcan's power when the dying hero touches his face, transferring Vulcan's power through a sort of tattoo. The tat is supposed to go on the new Son of Vulcan's chest, to facilitate secret identifying, but because the transfer is rushed, Mickey ends up with a brightly glowing hand-shaped mark right on his face.
 * Smaxx from Top Ten. A tattoo unwittingly left on his chest by a dying princess is the focus of much power-usage.
 * Doctor Strange has an ankh which will appear on his forehead if he is close to Death, or whenever he most needs an affirmation of life.
 * Aqualad II possesses Atlantean tattoos that glow when he uses his hydrokinesis.

Literature

 * In The Death Gate Cycle book series, a magician race called the Patryns uses tattoos for protection, amongst other things.
 * Thieves' World stories. The Adepts of the Blue Star had a blue star tattooed on their foreheads as the symbol (and price) of their powers. It glowed when the wearer felt strong emotions.
 * The Black Tattoo. And it was pretty darn creepy.
 * Junichiro Tanizaki's The Tattooer, a short story wherein a sadistic artist drugs a young geisha and tattoos a black widow spider on her back, thus releasing the cruel seductress hidden within her.
 * Eugenie Markham of Richelle Mead's Dark Swan series has multiple tattoos, most of which invoke the powers of the assorted deities she uses to enhance her magical abilities.
 * The fledgling vampyres get a crescent moon on their forehead in The House of Night. When it fills in completely, they have finished the 'change'. The main character Zoey Redbird's tattoo has already filled in of course, along with her getting various others when she gets her numerous special abilities.
 * Jennifer Lynn Barnes' novel Tattoo is about this. A woman from The Little Shop That Wasn't There Yesterday gives a girl named Bailey and her friends some stick-on tattoos that last for a week. Each of them gets a different power for the time they have their tattoos, though they don't know this when they get them.
 * Mr. Dark, the Big Bad of Something Wicked This Way Comes, controls the other carnies this way.
 * Gorlist, drow warrior from novels of Elaine Cunningham, has a dragon tattoo. Its glow indicated the presence of a dragon somewhere around, as well as its kind (which is needed to prepare for the encounter).
 * The Charter Mages in Garth Nix's Old Kingdom series. Among other unspecified things, the forehead marks allow "uncorrupted" Charter Mages to identify each other with a touch.
 * Cassandra Palmer from Karen Chance's Touch The Dark has a pentacle tattoo on her back that's a ward.
 * The Shadowhunters from The Mortal Instruments trilogy have the ability to carve (usually temporary, occasionally permanent) tattoos on themselves, giving them a variety of abilities, such as Super Strength, Super Speed, etc. However, not all of these are good.
 * The Imperium from The Grimnoir Chronicles brand kanji onto their operatives that enhance physical attributes as well as superpowers. The good guys know some that weaken captives and apply them in ash.
 * The Fallen's protagonist Aaron has this whenever he activates his angelic powers.
 * The protagonist of The Warded Man and The Desert Spear by Peter V. Brett covered himself in magical wards, each of which had a different power.
 * Shade from Dark Life is a variation.
 * The half-vampire members of the Fellowship of St. Giles in The Dresden Files have tattoos that indicate how much they are utilizing their vampiric powers, and thus how close they are to losing control.
 * Members of magically-inclined families in Collegia Magica are required to bear a tattoo of their family crest on the back of the left hand, whether they themselves are magically talented or not.
 * Cabaline wizards in Doctrine of Labyrinths are tattooed from elbow to knuckle as a display of their power and status.
 * A variant appears in Burying the Shadow involving dyeing the teeth as a visible sign of someone's powers. Soulscapers dye their teeth pink. Scryers dye their teeth indigo.

Live Action TV

 * Gabrielle's back tattoo in the Xena: Warrior Princess finale, which only glows once, but protects her from a fireball that would've seriously injured or killed her.
 * The tattoos of the Checkmate Four in Kamen Rider Kiva
 * In The Invisible Man, Darien's quicksilver Indicator tattoo on his wrist. Doubles as Mark of the Beast, as when it's red it means he's in the throes of quicksilver madness.
 * Played straight in Heroes with Nikki/Jessica.
 * This was the point of Tattooed Teenage Alien Fighters From Beverly Hills, an early 90's knock off of Mighty Morphin Power Rangers. I'm somewhat ashamed I remember it.
 * The tattoos that Lindsay gets in Angel to hide himself from the senior partners.
 * In the first season of Smallville when nearly every citizen in town got powers from Green Rocks, a gang has tattoos with meteor rock ink that allow them to pass through solid matter.
 * After being possessed by demons a few times, Sam and Dean get protective tattoos to stop it from happening again.

Tabletop Games

 * Dungeons and Dragons features a few options for functional body art.
 * Psionic users can create literal magic (well, psionic) tattoos.
 * In Forgotten Realms the tradition of Thayan Red Wizards teaches personal enhancements via tattoo, usually on their faces or shaved heads. The spell "Create Enchanted Tattoo" (AD&D) / "Create Magic Tattoo" (D&D3) makes a temporary empowered tattoo, and can be made permanent like other spells. It requires at least some degree of tattoo skill.
 * The Al-Qadim spell Tattoo of Power allows the caster to make a single-use tattoo with another spell -- just like writing a magical scroll, but implanted in the skin and discharged by touch and command word instead of reading; also requires the caster learn tattooing as such.
 * 3e Forgotten Realms Sourcebook Lords of Darkness has Tattoo Magic as item creation feat (mostly, for Red Wizards) -- this variety holds an arbitrary low-level spell affecting the bearer, is touch-activated and counts as a magical item worn on the inscribed body part.
 * Dragonmarks in Eberron. Well, halfway between Power Tattoo and Good Scars, Evil Scars.
 * Not to mention the new Spellscarred option in Forgotten Realms 4e, those affected by the spellplague (but not completely monster-ized) usually have the spellscar somewhere on the body. It tends to glow with blue fire when activated.
 * There's also the Tattooed Monk prestige class.
 * 3rd Edition supplement Relics & Rituals. Tattoo magic allows useful tattoos to be implanted into the user's skin and activated as needed. They include Chardun's Might (+4 to Strength and Dexterity), Coreans' Forge (Stoneskin spell on user) and Dragon (gain a dragon's breath weapon attack).
 * Caste marks appear on the foreheads of all Celestial Exalted if they spend peripheral Essence.
 * Sample character Kane Taoka in Scion has birthright tattoos, put on his body by the Titan Mikaboshi. One of them is a dragon he can summon at will, and two more are wings.
 * Electoos from Warhammer 40000 - it's a little unclear exactly what they do. Sometimes they are simple rank identifiers, whilst other authors use them as remote access keys, or even cybernetic circuitry.
 * In Demon: The Fallen, a tattoo that you can change at will is something humans have been known to make a Deal with the Devil to obtain.

Video Games

 * Jen in Primal has a circular design on her back that glows when she adopts various demonic forms. We're told it's important, and nothing else.
 * has a similar mark on his arm, although it may be just an ordinary tattoo.
 * One real life fan had a copy of Jen's tattoo done on his back.
 * The mark of the Triforce in some The Legend of Zelda games, which generally appear on the back of the dominant hand.
 * Not to mention the Fierce Deity form's facial tattoos from Majoras Mask.
 * Used literally in Planescape: Torment where Tattoos are one of the main pieces of equipment and confer numerous benefits on their wearer, as well as some playing a part in the plot.
 * In addition, one of the Nameless One's non-equipment tattoos is the Symbol of Torment itself, a physical manifestation of pain that he always bears, even if he forgets it's there.
 * Most of the palms in Kid Icarus: Uprising are this.
 * Heraldry in the Star Ocean series, the equivalent of magic, uses symbols drawn on the body.
 * The Mystics in Legaia II: Duel Saga all have tattoo-like birthmarks on their body. One of them, of course, has it somewhere that doesn't get shown.
 * The Hero Lang and Big Bad Avalon have their tattoos in visible sight (Lang's a bit too open about his). Shrinking Violet and Magical Girl Maya shyly refuses to reveal the location of her tattoo. Another character almost too eagerly explains the location of her tattoo. And nobody cares where Kazan's is. Too bad for him. And the other three mystics are minor villains, so it's not even brought up with them.
 * Digital Devil Saga has the Atma Marks as this. Bonus points because you can get one ANYWHERE on the body and the transformation pose has the character reaching out to touch it or show it off (hint: Jinana has hers on one of her butt cheeks).
 * Likewise, in Nocturne, the main character gets glowy sorta-power-tattoos all over his body, "sorta" in that they're a natural part of his demon body.
 * Shanoa of Castlevania has a nice set of three Power Tattoos, one on each upper arm and a large one on her back, which use Glyphs to cast her spells.
 * When Jin Kazama of Tekken becomes Devil Jin, he grows several Power Tattoos on his chest and especially forehead.
 * The Rood Inverse tattoo of Vagrant Story is quite literally a Power Tattoo, as it unlocks the power of Lea Monde and grants its user complete control over the city and its spirits. It makes Sydney effectively immortal.  Needless to say, the thing is practically Sealed Evil in a Can. Which is why they need Ashley...
 * The Noise in The World Ends With You all have tattoos which make up part of their bodies. In a particular example, the Psychedelifox, Ambiefox, and Progfox, who can steadily gain extra tattoo-tails during battle, which in turn allow them to do more vicious attacks.
 * Although never seen due to graphics limitations, enemy mages in Baldur's Gate 2 have these. They operate as an improved Contingency spell granting the ability to simultaneously cast multiple spells of any level.
 * Fate/stay night magi generally all have a Magic Crest of one sort or the other. It's a mixed blessing: it tends to make you better at whatever branch of magic that Crest is based on and some have additional powers such as providing mana for usage or However, they bind you and drastically limit your options. Tohsaka is somewhat jealous that Shirou doesn't have one and doesn't think he should ever get one. There's another type of crest the Magic Association gives but this one sucks even worse because all it does is mark you as too valuable to let you possibly run away.
 * The Tsoo from City of Heroes gain their powers from these.
 * In Final Fantasy XIII, l'cie have "the mark of a l'cie", which varies in design based on the fal'cie that chose them. It glows when they use magic or summon Eidolons, and changes over time to serve as a sort of countdown. If the l'cie doesn't complete their focus before it finishes changing, they become a cie'th, basically an undying inhuman monster.
 * In Prince of Persia: The Two Thrones, the Prince becomes infected by the Sands of Time, and occasionally transforms into a unique being known as the Dark Prince, which functions as a Super-Powered Evil Side. His whole body is covered by glowing tattoos while in this state. He also has normal tattoos when he isn't transformed.
 * Almalexia in The Elder Scrolls III: Morrowind.
 * These act as powerups of a sort in Clive Barker's Undying.
 * Beasts can turn into a large humanoid monster if they get a special kind of tattoo, known as a Blast Badge.
 * Fable III has tattoos that start to glow as you gain more magic power and morality. And then there are glowing markings that appear on your clothes if you use flourish attacks, their amount are increased as you gain more magic power. If your morality is good, your tattoos glow blue, just like the tattoos of Maze in the first Fable.
 * In Rift, the Defiant faction's resident stouts canonically tattoo themselves heavily, both to commemorate their accomplishments and to help channel their elemental heritage. Unfortunately, while this can be seen on NPCs, it's not really an option for players.
 * In Golden Sun: Dark Dawn Himi of Yamatai has Facial Markings on her forehead that greatly resemble the Third Eye Stone. Conveniently, the Third Eye is what she needs to wake from her visions and extract useful knowledge from them.
 * Mysteriously, villain Blados has similar markings on his forehead. Their purpose is unknown, but speculated.
 * Neverwinter Nights 2: Ammon Jerro in the original campaign. Safiya in Mask of the Betrayer. In both cases, derived from the Red Wizards of Thay.
 * Dungeon Fighter Online: The Male Fighter's subclass, Nen Master, makes use of tattoos to harness the power of nen without having to devote time. According to the websight, these tattoos decrease someone's life span by several years.
 * The never-released game Tattoo Assassins revolved around fighters with magic tatoos. It isn't nearly as good as it sounds.

Web Comics

 * Zoe's cursed necklace tattoo in Sluggy Freelance fits the bill, though turning into a camel whenever someone says the magic word "shupid" is a power that very rarely benefits her. The tattoo itself is pretty inconvenient because her mother would blow a fuse if she ever saw it.
 * In Dan and Mab's Furry Adventures, Dan's clan mark finally manifests during his fourth battle with Dark Pegasus, indicating that he has exceeded some sort of power threshold.
 * In The Dragon Doctors this is actually subverted. Kili the shaman has such powerful spiritual sight that she'd lose her mind if it weren't for the tattoos that suppress her spirit vision.
 * Two Gunnerkrigg Court teachers got a magical tattoo giving remote access to the device that that protects from Renard's Body Surf and binds him. And have lots of other... highly useful functions, while they're at it.
 * Susan from El Goonish Shive has a mark shaped like Venus symbol on her back. She needs it to call magical weapons, but the specific shape was her own choice.
 * Dex, a background character, seemingly spontaneously develops Summon Magic in one story arc. Other characters realize the power was actually bestowed on him by an Immortal when they see that he has a marking like Susan's, in the shape of a fairy on his chest.
 * Later we find out that has a tattoo that makes him stronger, and  has one that lets her make things bigger. Both characters are unaware of the tattoos or the powers.
 * Graham in Wizard School receives a magical tattoo on his face while in a drunken stupor - making him look like "Rainbow F***ing Brite."

Web Original

 * How about a tattoo Familiar?
 * Talies from The Motley Two (as well as other Writer-Mages) has a rune inscribed on his palm that, apart from marking him as part of the order, gives him a sensitivity to the flow of magic.

Western Animation

 * In Avatar: The Last Airbender, the Air Nomads are tattooed with sky bison arrow marks along their chi paths when they master Airbending. Since Aang is the last Airbender alive, his tattoos are also a dead giveaway that he's the Avatar. They glow along with his eyes when he's in the Avatar State.
 * Also "Combustion Man" fires powerful beams from his third-eye tattoo.
 * Young Justice has the new Aqualad, whose arms are tattooed. They glow when he is using his hydrokinesis.

Real Life

 * Well, not exactly real life, but: watch this.
 * This must be why MMA fighters are so powerful.