Something for Everyone

"Lister: "What did you see?"

The Cat: "Oh, just some gorgeous chunk of loveliness!""

- Red Dwarf, Camille

Some artifacts or beings look like different things to different people. The basis for the differences ranges from your worst fear to your greatest sexual fantasy, a favorite memory, or extremely symbolic representations of your psyche. Although usually an inherent trait, sometimes it's a simple Master of Illusion trick, and the thing does have a "true form" once you break through it.

See also Empathic Shapeshifter, A Form You Are Comfortable With and Lie to The Beholder. Sounds like but has nothing to do with Taste the Rainbow.

Anime and Manga

 * In the movie End of Evangelion,
 * With one notable exception.
 * The Illusion Card from Cardcaptor Sakura has this effect, taking a form to each viewer depending on what frightens them the most or what they desire. For example, Sakura saw her mother, allowing the card to have a strong hold over her, while Tomoyo, anticlimactically, merely saw a food item because she was hungry.

Comic Books

 * Morpheus from The Sandman did this. He would appear as a cat for cats or Bast and appear human for humans. Desire, on the other hand, works like the Apple of Discord naturally.
 * Morpheus has some control over this. He appears to the Martian as a horrible monster (because that is what their God of Dreams looks like) but then switches to a less frightening form.
 * In descriptions it's directly stated that Desire will look whatever you desire the most, whether that is man, woman or something else. Making it appear an attractive, androgynous human just helps the reader to keep track of the character.
 * Galactus appears as a member of whatever species looks at him, probably to Retcon his human appearance into the realm of plausibility.
 * Elizabeth Chandra in Rising Stars.

Film

 * The "Holy Grail" in The Mists Of Avalon appears as a chalice which creates food - whichever food one person likes most.

Literature

 * The Apple of Discord in the Illuminatus! appears to you as your heart's desire.
 * The Lone Power from the Young Wizards series supposedly looks different to everyone. To Nita, he usually looked like a good looking but cruel red-haired man.
 * In Harry Potter, the love potion Amortentia smells like all the smeller's favorite smells, and the polyjuice potion has a different consistency depending on who it turns you into (Crabbe and Goyle's looks like mud, Harry's is gold, we don't see what Bellatrix's looks like but it apparently tastes terrible.) In addition, Boggarts appear as one's worst fear, Dementors cause victims to experience their worst memories, and the Mirror of Erised reflects one's greatest desire. Yeah, Rowling loves this trope.
 * The second half of the Firekeeper series of novels gives us the Meddler, a godlike trickster. Lacking a corporeal body, he creates a form through the minds of those around him. The end result is that every person sees him differently. Most saw him as a local man. Others, such as Firekeeper's wolf partner Blind Seer, saw another wolf like himself.
 * In the old Photon novels, the nature of the contest between The Interstellar Alliance and the Arrians was eventually revealed to be a The appearance of these two beings, as revealed in the novel In Search of Mom? Just like the viewer, right down to gender.
 * In the Worlds of Power novel of Blaster Master, The Plutonium Boss did the "worst fear" version. The images the players of the game see is something each fears most.
 * Pretty Poison, a succubus from the Nightside novels, appears as everyone's hottest sexual fantasy come to life.
 * Verra, a goddess from the Dragaera novels, sounds different to different people. When she speaks, each witness hears her say something that's relevant to them.
 * TV news reports in Purgatory, from Piers Anthony's Incarnations of Immortality series, customize themselves to the interests of whomever is watching them.
 * In Clive Barker's Weaveworld, the villain Shadwell, who considers himself the world's greatest salesman and schmoozer, is given an enchanted jacket by the sorceress Immacolata. The jacket can produce from its pockets the object most desired by whatever client Shadwell is trying to make a deal with.
 * Similarly utilized in Stephen King's Needful Things, but in the form of The Little Shop That Wasn't There Yesterday.

Live Action Television

 * The salt-vampire monster in "The Man Trap," an early episode of Star Trek the Original Series.
 * In the new Doctor Who series, psychic paper has whatever you're expecting written on it. This apparently works even on electronic locks.
 * Red Dwarf has Camille, a green blob who appeared as a person's "perfect partner." For Kryten, Lister and Rimmer, she appears as a feminine counterpart to the viewer. For the Cat, she appears as...the Cat. The Psirens use a power like this to suck people's brains out with straws.
 * In Babylon 5,.
 * In relative obscurity, the final season episode of Roseanne "Satan, Darling" had a Dream Sequence in which Roseanne met the Devil's Advocate, who looked like her in red. It claimed, "I take on whatever form your subconscious chooses to give me. I almost came as a hamburger."
 * Subverted in Angel. The big bad, Jasmine, uses magic to make herself Awesome In The Eyes Of Others, otherwise she appears as a gross slimy thing. Connor, supposedly a good guy, thinks there's nothing wrong with the gross slimy thing (he wasn't brainwashed) because that's what he grew up with. Gross.

Video Games

 * In the unbelievably obscure 1990s PC game Commander Blood, the much-coveted Ondoyants appear as sexually attractive to everyone.
 * The monsters of Silent Hill appear as appropriate dark reflections of a person's psyche.
 * Grandia II included berries that taste like whatever the eater most fondly remembers eating.
 * The "Zone Of Nightmares" from Bionicle forces anyone who enters it to confront whatever they fear most.

Western Animation

 * In one episode of Pinky and The Brain the titular mice are placed into a sophisticated maze, including a room with a hologram meant to distract them by showing them whatever they most wanted to see. After unsuccessfully trying to find a secret area of the maze and coming full circle, Pinky states that what he most wants to see is a map of the maze, causing one to appear in front of them.

Web Original

 * SCP Foundation-056 always changes itself into a "better" version of whatever is viewing it, to the point that they can't even find out its natural form via remote observation because it just turns into a more expensive camera.
 * And SCP-959, who appears as whatever would distress the viewer the most. He's a really nice guy.