Knuckle Tattoos

"Ah, little lad, you're staring at my fingers. Would you like me to tell you the little story of right-hand/left-hand? The story of good and evil? H-A-T-E! It was with this left hand that old brother Cain struck the blow that laid his brother low. L-O-V-E! You see these fingers, dear hearts? These fingers has veins that run straight to the soul of man. The right hand, friends, the hand of love. Now watch, and I'll show you the story of life. Those fingers, dear hearts, is always a-warring and a-tugging, one agin t'other. Now watch 'em! Old brother left hand, left hand he's a fighting, and it looks like love's a goner. But wait a minute! Hot dog, love's a winning! Yessirree! It's love that's won, and old left hand hate is down for the count!"

- Preacher Harry Powell, The Night of the Hunter

Fingers. You've got four on each hand, plus thumbs. And the knuckles make a pretty good place to leave a tattoo. Ideally, a four-letter word. Maybe a second one on the other hand.

Compare Good Scars Evil Scars.

And no, a tattoo of Knuckles doesn't count.

Anime and Manga

 * Trafalgar Law in One Piece has "DETH" tattooed on his left hand knuckles. Later, it is changed to match what the anime had.
 * In the anime it was changed to say "DEATH", and now includes his thumb.

Film

 * The Trope Maker, Trope Codifier, and probably Ur-example (in media at least) is, of course, Robert Mitchum's character in The Night of the Hunter, who has "Love" and "Hate", and most examples since are Shout Outs.
 * Not exactly tattoos, but in Do The Right Thing, Radio Raheem has the four-fingered ring version of the knuckle tattoo. He evens says the page quote in one scene.
 * Buffalo Bill in The Silence of the Lambs
 * Eddie (Meat Loaf) in The Rocky Horror Picture Show, although it looks like he just wrote it on in pen.
 * In The Last Remake of Beau Geste, the sadistic sergeant played by Peter Ustinov has "Hate" tattooed on one hand -- and "Loathe" on the other.
 * The Blues Brothers each have their names on their knuckles. Elwood's name actually spills onto his other hand.
 * Old Joe Plaice from Master and Commander has "Hold Fast" tattooed on his knuckles. This is a tattoo that was common on sailing ships in the old days. So hooray for Truth in Television.
 * The a Team has B.A. sporting the words "Pity" and "Fool" on his knuckles.
 * Angel Guzman from Stand and Deliver.
 * The Skinheads in This Is England, or at least the nationalist faction, have crosses tattooed on their left middle finger knuckles. In one scene, the leader of the gang gives Shaun one with a safety pin.

Literature

 * In Discworld, one of Cohen's barbarian horde has "Hate" tattooed on both knuckles.
 * Harry King from Discworld has gold rings spelling his name, in the spirit of this trope. In case you wondered, yes, that's nine letters; he's missing one finger.
 * One of the bikers in Good Omens is mentioned to have 'Love' and 'Hate' tattooed on their knuckles. Another has 'Fish' and 'Chip'.
 * Bigmac has "LOVE" and "HAT" (the "E" keeps rubbing off) written on his knuckles in biro. Yup, Terry Pratchett loves this trope.
 * Seen in this fan illustration of one of John Hodgman's 700 hobos.
 * One of the bullies in the first Molly Moon book has KING GORD tattooed on his knuckles.
 * In Monster Hunter Vendetta, a truck driver that's an innocent victim of a monster rampage has "LOVE" and "HATE" tattooed on his knuckles. Later, is seen with "HATE" on the knuckles of his left hand.

Live Action Television

 * In The League of Gentlemen, the town vicar gets these tattoos around the beginning of the second season.
 * In a dream Jerry has on Seinfeld, Uncle Leo was in prison and had "Hello Jerry" tattooed across his knuckles.
 * Parodied with the The Now Show promotional image: reading left to right, we have written on the fists "THE", "NOW" and "SHOW"; then the last hand is opened up, with (I think) "On Fridays 6.30 BBC Radio 4" on the palm.
 * The ads for Ace of Cakes feature Duff baring knuckle tattoos of "BAKE" "CAKE", but he revealed that they're not only fake, but they had to use a hand model because his own knuckles were too hairy.
 * Jerri Blank of Strangers With Candy has "HARD" and "LUCK." According to Amy Sedaris, for some episodes the L was changed to an F.
 * Charlie in Lost writes various things on his knuckle bandages, such as "FATE".
 * Vince on Sons of Guns has "LIVE FREE" prominently displayed on his knuckles.

Music

 * "Death or Glory" by The Clash has a probable Shout Out in "Love 'n' hate tattooed across the knuckles of his hands/ Hands that slap his kids around 'cuz they don't understand."
 * The cover art of The Pogues' album Peace and Love features a man with those very words across his knuckles. Both words fit by virtue of him having six fingers on his right hand.
 * Ozzy Osbourne has "OZZY" written on his left knuckles. He did them in jail with shoe polish.
 * Parodied to the extreme with the music video of the song Pork and Beans by Weezer wherein at one point in the video several lines of lyrics are written all over one of the band members hands and flashed in time with the lyrics. That's a pastiche of Daft Hands, a viral video where the same thing was done with "Harder, Better, Faster, Stronger" by Daft Punk.
 * Crazy Awesome singer Diamanda Galás has "We Are All HIV+" tattooed on the knuckles of one hand.
 * From the Nick Cave song "The Mercy Seat:" "Like my good hand I/tattooed EVIL across its brothers fist."
 * Frank Iero of My Chemical Romance has HALLOWEEN tattooed across his knuckles (the double L being on one finger), representing the day he was born.
 * Oli Sykes, frontman of Bring Me the Horizon, has "Drop Dead" (also the name of his clothing line) tattooed across his knuckles.
 * Josh Homme, lead singer of "Queens of the Stone Age" has the name of his grandparents, Cap and Cam, tattooed on his knuckles
 * Tony Perry of Pierce the Veil has "STAR WARS" tattooed on his knuckles and "JEDI SITH" below them.
 * Dallas Green, of Alexisonfire and City and Colour fame, has "True Love" tattooed on his knuckles.

Professional Wrestling

 * CM Punk has "Drug Free" tattooed across his knuckles, as he is Straight Edge.
 * Sterling James Keenan (AKA Corey Graves in WWE developmental FCW) has "Stay Down" tattooed across his knuckles. I wonder if he ever asked anybody if they want to buy a vowel...

Video Games

 * Jack in Mass Effect 2 has "DEATH" tattooed on the knuckles and thumb of her right hand. The tattoos can be seen during the conclusion of Jack's loyalty mission, when the camera cuts to a close-up of her fiddling with the detonator in agitation, showing her hands clearly.
 * Sort-of, but one finger: On the cover of Mercenaries 2: World In Flames, if you look closely enough, Mattias has P-A-Y tattooed(carved?) on his middle finger, though it's never used.
 * One baddie in the FMV game based on Johnny Mnemonic had GAME OVER tattooed on his knuckles.

Web Original

 * Homestar Runner: Strong Bad writes "Deleted" on his knuckles, but he writes it backwards, so that when he punches Homestar, the ink will come off and leave a big "Deleted" on Homestar's face.
 * The Battle for Wesnoth has Bilingual Bonus Knuckle Tattoos on the Dwarvish Ulfserker/Berseker portrait - the runes read love and hate.
 * Wooley/Matt has the traditional "Love" and "Hate" tattoos in an episode of Fighterpedia about grappling in fighting games, but they're fake.

Webcomics

 * King Radical, a mafia boss in The Adventures of Dr. McNinja, has "MOST RAD." tattooed across his knuckles.

Western Animation

 * The "Cape Feare" episode of The Simpsons, Sideshow Bob has "LUV" and "HĀT", because he only has three fingers on each hand. This episode was primarily a parody of Cape Fear, which also starred Robert Mitchum.
 * Ren and Stimpy: Stimpy has Love and Hate tattooed inside his lips, like a racehorse.
 * Lilo and Stitch has Mr. Bubbles, who has "Cobra" (implied to be his first name) tattooed on his knuckles. One of the few examples to use the thumb.
 * The host of Bust 'Em from the Phineas and Ferb episode "Leave the Busting to Us!" has "Bust" and "Them" drawn on her knuckles, and did a (slightly mangled) full-speech Shout Out to The Night of the Hunter.

Real Life

 * This website demonstrated just how much this is Truth in Television
 * Parodied in one design by Toy Machine skateboards had cartoon knuckles with the company name tattooed on them. First hand had three fingers, the second seven.
 * Kat Von D, tattoo artist, and cast member of Miami Ink had various logos tattooed on her knuckles, as probably many other of the artists and customers on the show. Also, the shop owners' bar LOVE HATE seems to be a reference to the classical knuckle tattoos.
 * You can buy a whole darn set of temporary knuckle tattoos now.
 * Trace Cyrus has STAY GOLD, as a possible Shout Out to The Outsiders.
 * Basketball player Chris "Birdman" Andersen has "SCREW YOU" across his knuckles.