This character is an expert in a skill that has no practical use for them. It may be a cool, weird, fun, or even astonishing skill, but it's essentially pointless for them to have, or other characters are convinced the skill is totally useless.
Tropes Are Flexible, so this skill might turn out to be useful in a rare or oddly specific situation, like a balancing-chopsticks-on-your-nose competition, and could even end up saving the day. This is not an Audience Reaction: playing an instrument, knowing a trade skill, or having some other useful ability is only this trope when it's treated as useless for the character In-Universe.
Sometimes, writers will establish a character having this skill early in the work and then use the apparently useless skill in an important way later on so that no detail is pointless. Other times, especially in a Long Runner, established characters suddenly reveal their useless skill as a means of Character Development or to reveal Hidden Depths. For Main Characters, this can help to develop their backstory or just show their quirkiness. It can also flesh out supporting characters without diverting too much of the narrative focus to them.
This kind of skill can also be used as part of a joke, especially if the other characters never asked about it. If the character is an expert in multiple useless skills, they might be doubling as the Plucky Comic Relief. And if this character is a superhero, whose powers are not themselves useless, then they may be a Super Zero.
Compare What Kind of Lame Power Is Heart, Anyway? when the useless skill is a Stock Superpower or supernatural ability. Compare and contrast Useless Superpowers, which aren't framed as useless but which the story prevents the character from using; and This Looks Like a Job for Aquaman, when otherwise useless powers become useful in a very specific situation.
This trope overlaps with Chekhov's Skill when a situation arises for a character to use a skill that was previously considered useless. See also A Degree in Useless when a character's post-secondary education is treated like this.
- Doraemon: Nobita can create shapes with strings and rubber bands (called ayatori). It's one of the few things he can do well, and the fact it never sees any meaningful use is usually Played for Laughs.
- Sket Dance: The other characters mercilessly point out how boring Bossun's special ability to "concentrate really well" is.
- Yuragi-sou no Yuuna-san: Kogarashi Fuyuzora picked up a large number of mostly useless skills from being possessed by multiple spirits when he was young, including ping-pong, manga illustration, and free diving. These are mostly treated as useless at first but just happen to become handy later on.
- Fantastic Four: Willie Lumpkin the mailman jokingly suggests that he should join the Fantastic Four because of his special ability to wiggle his ears.
- Donald Duck: In one comic, Donald is put in a machine meant to determine his greatest aptitude, and it turns out that he has the innate gift for snake charming. He spends the rest of the stories moping about this trick of fate, only for the skill to be useful when he gets attacked by a giant snake.
- The Breakfast Club:
- Claire demonstrates her ability to apply lip color by tucking into her bra and rubbing her mouth against it.
- Without ever demonstrating it, Allison claims that she can write, eat, and play "Heart and Soul" on the piano with her toes.
- The Long Dark Tea-Time of the Soul: A girl in a sanitarium spends all day reciting letters and numbers. Her doctors have figured out that she's accurately reciting the New York Stock Exchange daily trades in chronological order. However, she does it 24 hours after it happens, so the doctors think it's useless — unlike if she were doing it 24 hours in advance. Thus, they don't really care why she's doing it. They even suspect that she's faking it by somehow getting her hands on the numbers and memorizing them to repeat the next day.
- In Doctor Who, when the Eleventh Doctor is asked whether he has an actual doctorate, he claims to have a legitimate one in cheese making.
- Hero System: Discussed where the 6th Edition rulebook specifically asks GMs not to ask players to spend points on useless skills and abilities.
- Dungeons & Dragons: 3rd Edition characters can invest in "Craft" and "Profession" skills, some of which are so specific and so useless to adventurers that they're usually only of use to NPCs and as prerequisites for certain obscure Prestige Classes. For example, the Archdevil Mammon, Lord of the Third Circle of Hell, happens to be a fantastically skilled bookkeeper.
- Pathfinder uses the Craft and Profession skills from Dungeons & Dragons, but lists the most common types of crafts and professions in the skill description. The Unchained expansion adds options to become even more specialized in those skills, though they remain of similarly limited value to adventurers. This varies enormously with the specifics; there are lots of applications for being a skilled sailor or engineer in an adventure, but your baking skill probably won't be called on.
- Shadowrun: ''Player Characters get free skill points for things called 'knowledge skills', which includes things like former job experience, hobbies, hometown knowledge, etc. Knowledge skills tend to come into play rarely if at all, and can include things like knowledge of hacker havens, the ability to speak fluent Esperanto, or a near-encyclopedic knowledge of the music of Maria Mercurial.
- The Pirates of Penzance: Major-General Stanley introduces himself with the iconic Major General Song in which he lists such useless and/or absurd talents like humming a fugue, writing a washing bill in Babylonic cuneiform or telling at sight a Mauser rifle from a javelin. Finally, he admits he doesn't have much knowledge a military man should have.
- Pokémon: Magikarp is infamous for starting out with only one ability, Splash, which has no effect whatsoever. It takes considerable patience to train it to the point where it can learn a useful move like Tackle.
- Dan and Mab's Furry Adventures: The Succubus and Incubus Academy has several courses that seem to specifically teach useless skills. Such courses mainly serve as excuses for the succubi and incubi to stay in school for as long as they want, since they're mostly immortal. Abel is a prime example and gets called out on it, to which he replies that grass-growing is "a rewarding and therapeutic activity."
- The Order of the Stick:
- When the Order first gets horses, Roy Greenhilt is forced to admit that he studied goat herding instead of horseback riding because "It seemed like an easy A." He also gets ribbed for having studied architecture and engineering in Fighter College, though he does use that knowledge to win a fight.
- Belkar's training as a gourmet chef is of little use to him as an adventurer — not even as Team Chef, since he lacks the ingredients or facilities necessary for gourmet cuisine and refuses to cut corners.
- xkcd: "Every Major's Terrible" is a Take That! to nearly every academic major for training students to have completely useless skills and knowledge. The only one not insulted is engineering.
Though physics seems to promise you a Richard Feynman-like career, the wiki page for "Physics Major" redirects to "Engineer".
- Things Mr. Welch Is No Longer Allowed to Do in an RPG: Exaggerated and overlaps with Master of None:
5. Not allowed to blow all my skill points on 1pt professional skills.
- "Underwater basket weaving" is an idiomatic phrase that means "a course or major that is absurd, useless, or completely irrelevant." It's used either in a pejorative sense or in the opposite sense. For example, calling the social sciences "underwater basket weaving subjects" versus avoiding singling out any specific major.