Equipment Spoiler

A video game trope found mostly in RPGs. Whether it's something you buy in a shop, find in a dungeon, or loot from an enemy's corpse, The Law of Conservation of Detail guarantees that it'll be of some use for someone in your party.

So what does it mean, when you find a giant axe that's too big for any of the characters to wield? Naturally, that the Big Guy is well on his way to join the party. Alternatively, one of the existing characters will get a Plot Relevant Power Up and gain the ability to use such weapons.

This trope usually appears in Eastern-style RPGs, in games where every character has a set type of weapon only they can use. When the game allows choosing player character's class, items usually will be placed in a way that ensures every class will find something useful for them ever so often. In such cases the trope can still occur, when an item is described as being useful for races or classes that are currently unavailable to the player.

Often, this trope is a big clue to the existence of a Hidden Character. See also Interface Spoiler, where existence of a character, item or power-up is suggested by the interface itself.

Note, that this trope only applies to items that are clearly treated as usable by the game's system. A mysterious Plot Coupon that may or may not be crucial for defeating the Big Bad doesn't count.

The common ways to avert this involve either plainly hiding the item until needed (it's not available at the start, but is script-triggered) or pushing aside The Law of Conservation of Detail (hide it between more instances of a Joke Item, Lethal Joke Item, useless eye-candy or something mediocre with extra eye candy on top).

Videogames
"I am happy beyond belief to finally have access to a Hex trading post. Although I'm not sure why they think we'd be interested in throwing knives."
 * An interesting one in Tales of Symphonia. There's a point in the game where your party seems to be killed off one by one. During that sequence, you find... a new weapon equippable only by one of the party members that already died. Spoils the moment a bit.
 * In Final Fantasy IV, you can find throwing stars for Edge in Eblan Cave before he joins the party at the end.
 * Similarly, in Final Fantasy VI, you can find shops that sell ninja scrolls and weapons in areas where Shadow can join the party.
 * In Final Fantasy VII, you may find a weapon for Vincent way before you can recruit him. And even then he and Yuffie are Hidden Characters, so you'll be encountering better and better weapons for them even if you miss them.
 * Averted at one point early in the game where you can find Cait Sith's ultimate weapon, but Cloud leaves it be because no one in your party has any use for a megaphone at that point and he doesn't even think anyone could use one as a weapon (unlike Yuffie and Vincent's gear).
 * In Final Fantasy VIII, a Weapons Monthly issue describing Rinoa and Irvine's weapons can be found before either of them is introduced (Rinoa does appear, but you don't learn who she is at that point).
 * You could also buy ammo for Irvine's gun before you met him. Rather annoying, considering that Squall's weapon was a Gun Blade, which contrary to what one would assume, didn't use any ammo at all.
 * In Planescape Torment oculars "usable by Modrons" drop from enemies all around the maze where you can find a Hidden Character of that race if you look hard enough.
 * Used in MARDEK in an interesting way:
 * Some monsters in Chapter 2 drop weapons that are not usable by anyone. You can carry them over to the next chapter... only to discover that most of them are starting weapons for the new characters.
 * In Chapter 3 you can buy a weapon usable only by a character that's considered missing-in-action as of second chapter's ending. It sprouted fan speculations about the character returning in a future installment.
 * Chrono Trigger has a merchant selling you scythes shortly before.
 * In Baten Kaitos you can find knuckle attacks before Savyna shows up.
 * In Warhammer 40000 Dawn of War 2 you can find pieces of armour for the Dreadnought way before you get one. Not enough information to guess that but once that happens, if you are familiar with the Warhammer 40k lore enough to know what exactly dreadnoughts are, you already know who will be piloting the one in your party.
 * Subverted in Fire Emblem: Mystery of the Emblem's Book 2: You can get a few axes but never get an axe user; you're supposed to sell them for cash. Averted in the remake, which features playable axe users and replaces those bonus axes with simply getting bonus money.
 * In Last Scenario, you will sometimes find weapons of a type that isn't used by any of your characters yet at a hex tile trading post. Lampshaded in Keltena's Let's Play:


 * Mass Effect:
 * In the first game, you can buy krogan, quarian, and turian armor before you meet Wrex, Garrus, or Tali.
 * In the second game, you can acquire an upgrade for the "squadmates with geth shield technology" during Tali's loyalty mission, before you meet up with Legion.
 * In Luminous Arc 2, the endgame quests give you various characters' best weapons. There's absolutely nothing to stop you from getting the weapons of a character you get even later in the game.
 * Subverted in Shining Force II, where Talos can drop his sword, which can only be used by the Giant class. No Giant ever joins the team.
 * Subverted in Betrayal At Krondor, though it's not quite as obvious as some examples. All swords and armor have a "racial mod" of either human, elven, or dwarven, granting a modest effectiveness bonus for the corresponding race. While you do have control of an elf and several humans throughout the game, you never get a single dwarf. The items are still perfectly usable, but the dwarven racial bonus on will never benefit you.
 * Surprisingly subverted in Diver Down--the very first shop sells an expensive suit of armor that no character will ever be able to equip (and this is a game that does not give Money for Nothing, so you will definitely regret purchasing it.)
 * In Radiant Historia, you can find claw-type weapons before you get a claw user, and buy weapons for a character who already left the party, spoiling that he would return eventually.

Non-videogame examples

 * Referenced in Adventurers when The Hero panics on discovering a shop that sells a weapon no one in the party uses, deducing that they must have missed a secret character..