Definitely Inuyasha. The main character's battle-happy brother Sesshomaru receives a sword that resurrects people. He begrudgingly carries it around and eventually resurrects Rin as a test to see if the sword works. The sword has a catch: it can only resurrect a person once so it can't save the people Sesshoumaru actually wants to save. Rin and Kohaku have died once before so he can't save them and Kagura's death dissolves her body, so he can't save her either. It turns out that he needed Tenseiga and the lessons Tenseiga forced him to learn to be able to finally achieve his desire (a combat sword of his very own that could match his vast power, the idea being that only a compassionate heart should wield great power otherwise that power would be grossly misused).
The Orihalcon Statue in the first arc (both novels, anime, and manga), which holds a powerful, magic-enhancing stone fragment. Lina happened to stumble across it on a treasure hunt, but the priest Rezo seeks it to cure his blind eyes. The end result is the resurrection of Shabranigdo, a demonic being that was split into pieces, and Lina and company have to defeat him.
Later on in the novels, there's the Blast Sword. Because he loses the Sword of Light for good in this version, Gourry needs a new one. He and Lina find a rusty old sword, and during the battle with Dynast Grausherra, it reveals itself as the Blast Sword, which is even more capable of fighting demonic beings than the Sword of Light.
In Yu-Gi-Oh! Kaiba gives Yugi his copy of Fiend's Sanctuary before the Final Battle with Marik in Battle City, knowing it's an effective weapon against the Winged Dragon of Ra but leaves it up to him to figure out how to use it; fortunately, he does.
A double subversion occurs in the two-part episode of Yu-Gi-Oh! GX where Judai duels Asuka (who is Brainwashed and Crazy due to the Society of Light). Both Fubuki and Manjyome give him cards before the duel starts, thinking that they might help him get through to her. When he first uses them, however, neither works at all. However, he is later able to use both to bypass Asuka's lockdown strategy and summon a monster that lets him destroy the White Veil card (a vital factor in the cult's hold over her) so the two cards do end up being useful... Just not in the way they were originally intended.
In Astérix in Britain, before setting out on the journey to Britain, Asterix takes some herbs from the Druid Getafix who says "Take some if you like." These herbs are eventually found out to be tea, which works as a Magic Feather for the British village they were out to save in their battle with the Romans.
Not long after Final Crisis, it's revealed that Darkseid cloned Batman several times. When the clones went crazy, they were all killed, except for one, just in the off chance that Darkseid ever needed a spare Batman corpse. Which he later used to fool the world into thinking Batman was dead.
Found in a Norwegian folktale about a princess who always had to have the last word. Three brothers are off to try their hand at winning the princess; the youngest is mocked for carrying around every piece of junk he finds. Youngest brother manages to stun the princess into silence by using the junk as props ([brother holds out goat horn] "I've never seen the like!" [brother gets out other goat horn] "Here you see the like, Princess.") and they live happily ever after.
In Mercer Mayer's version of East of the Sun and West of the Moon, the heroine meets a Plant Person of the forest, a Giant Fish of the ocean, and the North Wind, each of whom gives them a gift which she needs to use in order to defeat the Troll Princess: a bow and arrow from the king of the forest, a fish scale, and a tinderbox. In the last case, she needs to free her prince from a block of ice. The tinderbox burns the drapes, melting the ice, which douses the flames.
From Harry Potter and the Methods of Rationality: Dumbledore with great ceremony gives Harry... his father's rock and tells him to keep it with him at all times. It's just a big rock which is not special at all. The fact that it actually does come in useful, and the circumstances where it does, are seen as so suspicious in-universe that it completely changes the state of political alliances by bringing the Malfoys in under Harry's personal banner.
Galadriel's little phial (see literature below), moreso in the animated The Return of the King, where the phial just shows up in Sam's pocket — due to rights issues preventing them from telling anything set up in the first two books, which Ralph Bakshi had the rights to.
Sam: What's this? a vial. And what magic is in it to make it glow so? Handy, this thing...
Tia Dalma: Land is where you are safe, Jack Sparrow. And so you will carry land wit' you. Jack: ...this is a jar of dirt. Tia Dalma: Yes... Jack: Is it special dirt? Tia Dalma: If you don't want it, give it back. Jack: No!
Tia Dalma: Then it helps.
The Nine Pieces of Eight. The Pirate Lords were, to a man, skint broke.
Pintel: "Those are nine pieces of junk!"
Bootstrap's grungy knife as well. It seems an odd gift, but Bootstrap gives it to Will as if he knows he will need it and may never see him again. Will assumes he needs it to stab the heart. Ironic in hindsight.
The everyday items in Paycheck. Rare film example of a plot setup involving the character collecting otherwise useless everyday items, justified in that the character knew exactly what was going to happen in the future and when. Although why such a security conscious company would allow him, with their knowledge, to take a key card with him is anybody's guess.
In the short story its based on, its revealed that the machine wasn't just a viewer, it allowed one to extend a mechanical grasping arm through time to obtain objects. The protagonist uses it to grab the final MacGuffin out of the villain's hand at the climax, then his future-self pulls it out of his pocket.
In the Ewok Adventure TV movie, Mace is given a seemingly useless rock by Chief Chirpa. He discards it, but Wicket picks it up and gives it back to him, to Mace's dismay. Later when the group is trying to find the entrance to the Gorax's cave, Mace tries to use his blaster to make an opening, but it fails to destroy the rock. However, when he breaks open the little innocuous rock given to him by Chief Chirpa, a little arrowhead falls out and zips under a nearby boulder, which is revealed to be a secret entrance to the cave.
Done rather poorly in Troll 2, when Grandpa Seth hands Joshua a double-decker baloney sandwich, saying "take this, and only use it when you really need it". The last 5 minutes of the film may not be a good time to introduce a vital Chekhov's Gun.
Another iffy example happens in Van Helsing, when the monk-inventor sidekick introduces the hero to a seemingly vulgar stone that can produce a sudden burst of solar-like light. The monk-inventor insists he doesn't know why it could be helpful, despite knowing that they are going to travel to Transylvania to fight vampires who are vulnerable to day light, then says he is going to take it anyway. Three guesses about what specific item they use to escape a palace filled with vampires at night later on.
The Man Who Would be King: In the glory days of the British Raj in India, ex-soldier Peachey Carnehan (Michael Caine) steals a pocket watch from a well-dressed white man (Christopher Plummer as Rudyard Kipling) at a train station. Peachey sees the watch fob is a Masonic emblem and, being a Mason himself, "has" to return the watch, hopefully without giving away his thievery. He does (or thinks so) and thus meets Kipling. Later Peachey and Daniel Dravot (Sean Connery), also an ex-soldier and Peachey's fellow "gentleman-of-fortune", meet with Kipling and tell him of a grand adventure they are about to embark on. Later still, as they leave for this adventure, in an impulsive gesture Kipling gives the watch fob to Dravot. It later saves their lives.
Parodied in The Wrong Guy, where Nelson is given two tea bags and a sheet of wax paper and told that you can kill a man with them. When Nelson is attacked by the villain, he ineffectually waves the items around, as he has no idea how to use them.
Most of the Fighting Fantasy and Lone Wolf books qualify. Lone Wolf and the Fighting Fantasy series Sorcery!, being multi-part series rather than one-offs, are the most worrying with this — certain items might not come in handy for three books. Fighting Fantasy at least usually has no rules on how much you can carry. Lone Wolf is not so lenient.
To make things worse, Lone Wolf sometimes subverts this with items that look like they fit this trope but which serve no purpose at all, or even a few that are actively harmful. And because it's a gamebook with branching paths, sometimes you'll just miss the path where an item is supposed to be used, carrying it around for dozens of later books with no payoff.
Quite frequent in GrailQuest, though the items are often rather bizarre. Especially notable in book 3, The Gateway of Doom, which adds a Critical Encumbrance Failure aspect, and has Merlin lampshades the trope in the text:
Pip: Why should I want a gold braid, a joke book or a xylophone? Merlin: Why should you want a hammer or a saw? Pip: Because they might come in handy. Merlin: So might a gold braid, a joke book and a xylophone. Anything might come in handy in an adventure like this.
Her gift to Sam? A Box of Dirt with a seed in it. Galadriel specifically says it won't help Sam on his quest, but when he gets home. Given his vision in the Mirror, she has a fair idea of how it will be used.
Galadriel's little phial, too. The movie version implies that Galadriel knows it will be useful against Shelob, but the book, less so.
The Hobbit: Bilbo finds the One Ring by complete accident.
He crawled along for a good way, till suddenly his hand met what felt like a tiny ring of cold metal lying on the floor of the tunnel. It was a turning point in his career, but he did not know it. He put the ring in his pocket almost without thinking: "Certainly it did not seem of any particular use at the moment."
In Percy Jackson and the Olympians, the eponymous character is given a pen and told only to use it times of great need. It helps.Given that it's a pen that can turn into a sword... He then proceeds to whip it out at any possible time whatsoever, probably because he's a teenage boy who owns a pen that turns into a sword.
In the book Key to Rondo, Mimi's pendant and her lemon candy prove to be what the bad guys want, and the decoy.
As she leaves for a boat trip, Martine of Dolphin Song is given a plant by the old woman who's been teaching her about bush magic. Everyone teases her about it, until it proves to be the cure (the only cure on hand) for Man o' War stings. The best part is, the woman told her later that she just wanted it out of her garden.
In The Phantom Tollbooth, Milo is given gifts by many of the people he meets, and they all come in handy when he is facing the demons who live in the Mountains of Ignorance.
The Sirens of Titan features an interesting twist. The main character's son picks up a random piece of scrap metal during a factory tour on Mars. It becomes his lucky piece and he carries it with him everywhere for the rest of the book until they arrive on Titan itself. Turns out, this little piece of scrap is the replacement part the alien observer has been sitting around waiting for since before the dawn of humanity. It seems all of human history was guided (and perhaps even BEGUN) by his species remotely just to bring him this small piece of metal so he could continue his mission (which it turns out is just to say "Hi" to whoever lives on the far side of the universe). It's a bit of a downer realization, until one considers that with this delivery/quest complete, perhaps humanity will be free to pursue its own destiny.
In Jim Butcher's Spider-Man novel The Darkest Hours, Spider-Man asked Doctor Strange for his assistance in dealing with the Ancients, three malevolent beings related to Morlun (from the J. Michael Straczynski run). Strange refused, stating that doing so would undo the cosmic balance. He did arrange for his manservant Wong to prepare Spider-Man a sack lunch... which contained, along with a ham sandwich, three small stones which could be used to transport someone to an uninhabited dimension. After Spider-Man defeated the Ancients, Strange asked Wong what had happened to the stones, pretending not to know anything about their use.
Subverted most effectively in Brandon Sanderson's Mistborn trilogy - Vin's earring, her only memento of her mother which she has been wearing since the start of the first book, turns out to be the way the Big Bad has been influencing her all along.
Subverted in Katherine MacLean's Missing Man, where a guru gives George (the protagonist) a quarter, saying "I can see into the future a little. In two weeks if you don't have a quarter you'll probably die," and "Tape it to your skin and forget you have it." In fact, the quarter does become (hypothetically) useful... except that George, as instructed, forgets that he has it, and so never uses it.
In Whispering Nickel Idols, Garrett brings a bucket of kittens to Belinda's mob party, thinking he can get rid of a few by giving them away. (Morley lampshades how unlikely this is to work, but Garrett really doesn't want a bunch of cats in his house.) As it happens, the "kittens" are actually the Luck of A-Lat, whose presence soothes emotions and prevents a bloodbath at the gathering.
Common in live-action adventure games from the Dream Park series. Kevin's gift of a soot-covered rag in The Barsoom Project is a good example.
In Night Watch, Anton is Genre Savvy enough to know that any amulet Geser gives him will most likely be useful in the near future. Even a low-level Other is able to view his own probability lines. An old and powerful Great Other like Geser can do it a lot better. Why would you need an enchanted SIM card in Uzbekistan? Well, to block GPS tracking on your phone, of course, in case someone decides to cause an avalanche at your location. Why would battle mages like Anton and Alisher need rings that protect against fire, ice, poison, and vacuum when they can just use the Mage's Shield spell? Because those will happen to be the spells that their enemy will use, and the battle mages will have The Load to protect.
Emperor Mollusk versus The Sinister Brain by A. Lee Martinez. Mollusk keeps finding superfluous components in cybernetically-controlled organisms sent by the Brain to destroy him. The unusual thing is, all the components are based on his designs. The components eventually assemble into a device that plugs into a machine that shuts down the Brain and his cohorts, as part of a Batman Gambit arranged by Mollusk's future self, who's being held prisoner by the Brain.
Estate of Panic: The most successful contestant in the second of three rooms usually received an item that might have helped them in the third. For example, in the first episode a contestant was given a screwdriver, but had to figure out where to use it (on the A/C vents) to earn the extra money.
Parodied on Garth Marenghi's Darkplace, when ghostly Scots invade Darkplace Hospital: "What's this?" "Something that might come in handy."
Rather cruelly inverted in an episode of House, where they spend an entire episode looking for a cause for a young boy's ailment, only to discover that a piece of scrap metal used as a fob on his keychain was highly radioactive. Previously unrevealed to the audience, it had been randomly picked up by his father, a scrap dealer, and given to him as a Memento MacGuffin to remind him of his roots.
Played fairly straight in Merlin, episode "The Eye of the Phoenix", when the Fisher King hands Merlin the waterglobe and says "When all seems lost, this will show you the way."
Happens on Tracker when Mel finds both her grandmother's diary and the strange triangular object. She finds it a bit odd but dismisses it and nails it up as a decoration, and it's only later that the writing on it is ID'd as Vardian and they learn that it's the key to the underground vault, and that the diary's poetry was another key clue.
In the first episode of MythQuest, Alex (as Theseus) is given a ball of string to help him navigate the labyrinth of the Minotaur.
Grytpype-Thynne: Now, here's a screwdriver, a blindfold and a cucumber. Neddie Seagoon: Cucumber? Grytpype-Thynne: You've got to eat, haven't you? (it's actually a bomb)
In Richard Wagner's Siegfried, after Siegfried kills Fafner, he can understand the forest bird's song telling him to take the ring and helm. He doesn't know what they really are, but it keeps them out of the hands of Alberich and Mime. (Too bad that the ring is an Artifact of Doom...)
Many adventure and RPG games condition pack-ratting behavior as an inventory management pressure, especially if there are inventory limitations and/or economic necessities. Not all games give clues whether the items are useful for problem-solving, or at least for uncovering Easter Eggs, or just Vendor Trash or completely dead weight. Recently the games have gotten easier by simply making the "Handy" things undroppable/unsaleable, rather than more intuitive in their problem-solving application.
Standard policy for adventure games is that if it's not nailed down, take it, you'll need it. If it IS nailed down, find a way to remove the nails and take it. And take the nails too. Many, many early adventure games punished people for following this advice before realizing that it was a bad idea. For example, in Uninvited, picking up a certain seemingly important gem results in being demonically possessed about three turns later. Whoops.
All the old LucasArts adventure games have this. If you can pick it up, no matter how random and useless it seems, you will at some point need it. Unless it's a Red Herring. And sometimes even then, as The Secret of Monkey Island has proven.
An interesting case occurs in Escape from Monkey Island in the Swamp O' Time. Guybrush meets himself in the future, who gives the present-Guybrush several items and holds a conversation with him. Shortly after, present-Guybrush ends up on the other side of the encounter and must follow the exact same routine as before in order to avoid a Temporal Paradox and restart the area. One of the items is a pistol, which makes Guybrush excited to finally get one, only to have to give it away soon after. The items themselves are a part of an Ontological Time Loop, as they have never been created.
Monkey Island plays with this one. At one point in the first game, you can pick up a staple remover, which Guybrush remarks will probably come in handy. Like almost everything else you find, it is seemingly useless, until:
Not to mention a Rhinoceros' toenails; probably the same Quarrelsome Rhinoceros you hypnotized earlier.
The staple remover can also be combined with the flint to blow up the dam on Monkey Island. Since this puzzle can be solved with the spyglass and the sun, it makes at least one set of items (or resulting scenery) useless.
"A rubber chicken with a pulley in the middle... what possible use could that have?"
Not really useless in value, but the wedding ring in Tales of Monkey Island is given to you in Episode 2 and proceeds to uselessly sit in your inventory. It ends up being the solution to the final puzzle of Episode 5.
Every Infocom game includes at least one of these. The best is the piece of braided black string in Zork 2, which seems completely useless at first, but turns out to be the fuse necessary to make sure you can get away before the plastic explosive to blast open the locked box goes off, without which setting off the plastic explosive kills you automatically.
The two Discworld games, where there really are totally useless things to collect, albeit not many, making them more Red Herrings.
There are items like this all over the place in Alone In The Dark 1992, e.g. an Indian cover, a heavy statuette and others whose use isn't quite obvious at the beginning.
In Brain Dead 13, both times while trying to get away from the witches, Lance picks up an eyeball hanging on a rack for no discernible reason whatsoever. At the end of the game, he gets the idea to tie the two eyeballs together like a bola in order to stop a boss, but that still doesn't answer the question of why he picked up the eyeballs in the first place.
The trend in the series, since at least the second game, is that you will always get what you need to complete the next dungeon either in that dungeon, or right before it. This can become egregious at some points, like the trope picture. How lucky is it that you found that item right before flipping over blocks and pots from a short distance away became a vitality important ability? It's sometimes justified by the dungeons being carefully laid out trials, but just as often it isn't brought up. Did whoever designed the fire-temple in The Legend of Zelda: Ocarina of Time know that the switches would become rusted over, and that's why they left a hammer capable of pressing them for you to find, or was it just a coincidence?
At another point, you, again, get an item that immediately helps out in the trial afterwards. This time however, it seems to be that Link just decided to be smart after killing an enemy wielding a ball and chain and thinking "hey, this could probably break all that ice I can't get past". Doesn't explain why no other enemy in the game wields a ball and chain.
When replaying Silent Hill 1, you find a device in the 7-11 lookalike that is of no use unless you're at certain locations (e.g. the rooftop of the oxidised Midwich Elementary) through which you get the Alien ending and a raygun for the next replay.
During the main story, Harry comes across the elderly witch Dahlia Gillespie, who assumes The Mentor role and gives Harry two items: a rather sensible key to a locked drawbridge, and a more bewildering puzzle-box device, along with the cryptic explanation that "these will help you". It later turns out that she's deliberately being vague because she's setting Harry up as an Unwitting Pawn).
A very minor example occurs in Mass Effect 1 if you choose all the paragon interactions with the Asari Consort. She gives you a seemingly worthless trinket that you can later use on another planet, to discover a recording made by the protheans of early humanity (with some Experience Points and Credits of course).
In Asteka II Templo Del Sol (a.k.a. Tombs and Treasure), you get the lighter from the first room in the game, and it can't be used for anything until the last room in the game, where it's necessary to complete the game.
Final Fantasy I: You're given a Lute by Princess Sarah after you defeat Garland. This item does absolutely nothing until the final dungeon, where you play it to break a seal and move on. Remakes show your lead character playing it. The song? The Prelude.
In Final Fantasy IV, if you talk to Yang's wife at a certain point, she will give you a spoon. This turns out to be a thrown weapon, and the only weapon that does max damage against the final boss.
Earlier in the game, you get the FRYING PAN OF LOVE, no mere spoon, which is also a ridiculously strong throwing weapon. You're supposed to use the frying pan on Yang, and she'll give you the Spoon, which is an even better throwing weapon (the spoon is in later versions replaced with a knife).
At the start of Final Fantasy XII, the main character Vaan breaks into the Palace of Rabanastre to 'liberate' the treasure within from the imperials. However, thanks to well-times distractions, he only manages to steal a shiny rock. This turns out to be the Dusk Shard, which falls into enemy hands when Vaan is captured. In a subversion, it's the villain who nearly wins because of it — he attempts to use it to power a giant airship.
In Final Fantasy VIII, if Squall talks to Cid just before leaving for his first SeeD mission, Cid presents him with an old lamp which he says is a cursed item but might come in handy. The lamp has the Guardian Force Diablos sealed inside it.
In Ratchet & Clank: Tools of Destruction, The Plumber hands Ratchet a 3 3/4 Centicubit Hexagonal Washer saying "you never know when you'll need it." This item is utterly worthless throughout the game. As it turns out, it's used at the end to repair the Dimensionator and prevent it from destroying the galaxy.
The "Wand of Nagamar" in has no combat or utility value (though the combat messages could be entertaining). However it's required on the final Council Quest to provide an absurdly unlikely finale to The Naughty Sorceress.
The game has a considerable (and sporadically growing) number of such items, varying in degree of apparent uselessness, and has slowly begun to add skills of this type (such as the Disco Bandit skill "Gothy Handwave", which is Exactly What It Says on the Tin — and unlike other dance skills, does exactly what it does in real life).
Very few examples are actually handed to the player with the accompanying dialog, the rest of them Randomly Drops without drawing attention to their significance. The Amulet of Plot Significance which drops on the Penultimate Fantasy Airship is one subversion, but the Cid-likeCaptain Ersatz on the same ship gives you two items critical to completing that quest and The Very Definitely Final Dungeon.
After the Level 10 quest revamp, the Amulet of Plot Significance does help you on your quest, as it can be used to unlock the second level of the Giant's Castle.
Every game of Indiana Jones and His Desktop Adventures (an adventure game where the world and puzzles are randomly generated each time) should begin with Marcus giving you a briefing and giving you "something to get you going" — usually a priceless ancient artifact which inevitably turns out to be just the thing a NPC needs.
In the first Mata Nui Online Game, after the Po-Koro event, as a reward for helping the town, you are given an item, the "Po-Koro chisel" which seems to have absolutely no use, surprising in a game where every single item serves at least some purpose in one way or another. Flash-forward to the ending cutscenes of the game where Takua is fleeing from the newly-awakened Bohrok, and he discovers a device with an indentation that bears a staggering resemblance to the chisel. If you can't guess what happens next, you haven't been paying much attention.
One game that averted this was the original, which, due to having multiple characters and multiple endings, has many items that were worthless if you have the wrong party. It also has items that are completely worthless no matter what, such as the chainsaw, which has no fuel.
Interestingly, the sequel Day Of The Tentacle goes back to the traditional tactic of not only having every single item be used at least once, but if the item is small enough to be passed through time, it will be needed in another time.
The only item that's never used is the hubcap....and you can not pick it up.
A fortune cookie with gibberish on it. Contains the solution to a game of Simon in the last part of the game.
And, "in case all else fails, some body armor."
In Spellcasting 101, there is a book that is so good you can't put it down. Literally. Once it's in your inventory, you can't drop it. In the penultimate puzzle, you give it to the Big Bad, and since he can't put the book down, he can't activate the MacGuffin, as the activation buttons are on opposite sides of it, requiring the use of two free hands.
In The Orion Conspiracy, LaPaz will give Devlin keys to open the cupboard in Danny's room. Also, Ward will give you a rotten biscuit to spite you later on. In both cases, the items are immediately useful in some way.
Green Moon is full of items which seem initially useless but turn out to be necessary for spells or potions.
Parodied in Pokémon Black and White: the post game begins with Looker coming to your home to ask for help apprehending Team Plasma's 7 Sages. He then gives you a Super Rod (a fishing rod), and the player character's mother asks what help a fishing rod would be. After thinking for a minute he admits that it would be no help whatsoever.
Also seems to show up in Pokémon Gold and Silver and the remakes. The player's mother saves some of the money they earn and randomly buys items. She'll always say "I'm sure you'll find it useful" or something like that when she calls to tell you.
In Radiant Historia, the main character, Stocke, is given a seemingly useless book by his boss at the beginning of a mission.It ends up saving his life, and kickstarts the plot from there, by giving him the ability to travel to specific points in time.
In Casper: A Haunting 3D Challenge you collect fool's gold coins throughout the game. They appear useless until the final boss, where ghost Carrigan chases you around a maze and you can drop coins to distract her.
In the cancelled Warcraft Adventures: Lord of the Clans, Thrall has to chase vultures off of a wolf's corpse so he can grab the bladder and stash it in his pocket. Of course, you end up needing it later on, but one has to wonder what compelled him to pick up a (still full) bladder in the first place...
Parodied in the Dragon Tails RPG arc, in the same strip as But Thou Must, nonetheless. Uncle Sparky, the dragons' slobbish uncle, offers the heroes some help.
Uncle Sparky: I shall give you a half empty pizza box and a bag of garbage to take to the curb. May they be of aid to you on your journey.
Also, during an early adventure, Elan picked up a magic belt that can turn the wearer into the opposite gender. Some time later, Roy needed a way to sneak past the enemies without his weapon and Elan showed him the belt.
The above example later leads to a subversion of this trope, when we learn that at the time Roy had in his possession two potions, Shillelagh Oil and Delay Poison, which were exactly what he would have needed to escape the situation without having to done the belt of gender change, but he didn't think of it.
Problem Sleuth carries his precious cargo through the whole comic/game: four pieces of candy corn.
At the end of Episode 9 of The Mercury Men, Jack Yaeger gives Edward Borman his ray gun, implying he'll need it later.
Tends to happen a lot in The Questport Chronicles. During Year Two, the heroes find a bunch of junk, including an old spell, while searching for a different Plot Coupon; the spell becomes vitally important to retrieving the next Plot Coupon.
Subverted in an episode of Family Guy. After Quagmire has an affair with Cleveland's wife, Cleveland's swears revenge. Quagmire hires Mayor Adam West as a guard, but after failing to keep still, West decides to leave while giving Quagmire a banana and telling him "When the time comes, you'll know what to do." Later, when Cleveland is chasing him, Quagmire throws the banana... and it does nothing. The way the scene is set up to invoke the classic banana peel gag to viewers, but Quagmire forgot to peel the banana before throwing it.
One episode of Darkwing Duck is made up of a long string of characters literally saying "This could come in handy some day." It's an aged Darkwing telling his supposed origin story, and everything from his gas gun to his martial arts skills is given to him with this note from the repeated giver. And damned if they don't all get used in sequence in the course of about a minute.
As a parody or tribute to James Bond, Totally Spies! uses the exact same "three gadgets that each get used once" shtick.
Freakazoid!: "The Wrath of Guitierrez" had the eponymous hero needing a McGuffin to detach himself from a device on time to avoid deletion after an enemy sucked him into an Adventure Game. He needed certain items to help through his question, and lampshades the usual pixel-hunting with things like a bowl of soup he finds behind a suit of armor. He also lacks the usual invisible inventory, and towards the end of the game is carrying a huge armload of stuff.
In one episode of ReBoot, Season Three, Andr A Ia and Matrix are training a small team of citizens from a rundown system to play Games and win. The game in question is modeled after typical RPG fantasy quest games, and the character who reboots as a wizard finds a feather on the path. He sticks it in his pouch. One other character sarcastically remarks "Great. If we meet the user, you can tickle him to deletion." Later, the feather proves instrumental in getting the team inside the castle, as it allowed the wizard to give himself wings.