An object which is the embodiment or representation of the solid, happy relationship between two characters, or of an important memory or period in someone's life.
Sometimes it's as obvious as a piece of jewelry like an engagement/wedding ring, or a wedding video, or a photograph of a beloved, or a prized heirloom. It can also be a love note or just some small gift, such as a stuffed toy. It can even be a location, such as a childhood home or a favorite corner market, an old building imbued with poignant memories or an entire town. Such a memento can represent romantic partners, deep friendships, familial relationships or even esoteric connections. Whatever the item, and whatever the nature of the relationship, there is a symbolic yet very real form of Synchronization between the Memento MacGuffin and the relationship, and because of that, it tends to also be a Number One Dime.
These items tend to give a lot of exposition and, rather than being true MacGuffins, can play a central role in the plot. Unfortunately, they also tend to be rather luckless. On the other hand, if a character deliberately disposes of the item, it's because It's All Junk. Also, if the character acquires it through a very sad experience, it's a Tragic Keepsake that might be held during a Cradle of Loneliness.
If, however, a character's parents are conspicuous by their absence, or completely unknown, that "treasure" the character carts around with them is probably a specific type of Memento MacGuffin — the Orphan's Plot Trinket. Expect it to be important.
Pictured above: The star-shaped music box is a reminder of her link with Endymion and their past life together. At the end of the first season, she takes it out and shows it to him (who was brainwashed and crazy at the time) as a last resort. Pleading for him to remember who he was and how they loved each other long ago. It works, but the locket disappears and is never seen again afterwards.
Also near the end of the anime's first season, we have Minako/Venus's friend and Secret Keeper Katherina's locket. Venus finds it after Katherina has been forcibly turned into a youma, with the bonus of it having a picture of both girls inside. She then pleads with Usagi/Moon to spare Katherina and dis-possess her.
Princess Mononoke, The crystal necklace Ashitaka gets from his sister as a (permanent) farewell gift. He gives it to San as a token of affection/remembrance. She later stabs him with it in a fit of despair, but without serious consequences.
Yuri's blue pendant in Kyo Kara Maoh is a double whammy — it was given to him by his godfather, Conrad (and, in a variant of Lost Wedding Ring, Yuri panics when he loses it); but Conrad was entrusted with it by Julia... who is reincarnated as Yuri. The pendant therefore connects Yuri to two people (Conrad and Julia) and a memory (his past life).
Digimon Savers: Masaru's dogtag belonged to his father, who gave it to him the day he left on the Digital World expedition. It symbolizes manhood (what else?) and serves as a reminder of the ideal Masaru is always chasing.
Suzaku's pocketwatch (more accurately, his late father's pocketwatch), which symbolizes his being stuck in the past. When he leaves it behind during the first season's finale (with the body of the woman he loved, shot dead by his best friend), it's supposed to signal the fans that the kid gloves are off.
He also keeps his pin(?) designating him as Euphemia's knight, holding it introspectively and brandishing it at others as a symbol from time to time (notably in R2 episode 17).
And Rolo's locket, which was given to him by Lelouch. It symbolizes... the er, "brotherly friendship" between him and Lelouch.
Also, Euphemia's quill pen, which he keeps with him and uses to write. His cat Arthur is shown running off with it in R2 episode 5. Boy, he sure does have a lot of stuff on him.
Tohru's picture of her mother in Fruits Basket — she takes it everywhere, even addressing it as "Mom."
Duel Monsters trading cards are frequently used to this effect in Yu-Gi-Oh!. The first episode of the Duel Monsters anime revolves around Seto Kaiba forcibly wresting away Yugi's grandfather's Blue-Eyes White Dragon; he wouldn't sell it because it was a reminder of his friendship with Arthur Hopkins. Of course, the Blue Eyes White Dragon card is a Memento MacGuffin (or Tragic Keepsake, depending on how you look at the situation) for Kaiba himself, which is part of the reason why he wanted it so badly in the first place...For Kaiba, it was a weapon for domination in the card game. Only in the case of the duel against Isis/Ishizu did it become a Memento MacGuffin.
In Fullmetal Alchemist, Edward carries around a silver pocket watch given to him when he joined the military. In the inside of the watch he engraved the date 10.Oct.3, the day he burnt down his home, to remind him he can never turn back.
the full cyborgs Batou and Major Katsunagi have mementos from their pre-cyborg days: Batou's exercise weights, and the Major's watch. The watch does double duty as a straight-up MacGuffin as well: the Major accidentally left the watch at her house on the day she had to go into hiding, so Batou risks capture to retrieve the watch for her.
The sheet of song lyrics in Gravitation, the ones that Shuichi wrote and Yuki criticized. Presumably, Shuichi kept the original copy — it reappears at a key point at the end of the anime.
Ichika from Uta Kata keeps the mirror shard into which Manatsu changed in a drawer, together with Manatsu's beloved soap bubble pipe.
The three magical jewels in Sorcerer Stabber Orphen, specially Cleao's sword. That one was a heirloom of the Everlasting family, and Cleao tags along with Orphen and Majik to make sure Orphen will give it a good use.
In Madoka Magica, Homura's weapon of choice changes to a bow in the last episode. Previously it was a buckler, to symbolize her wish to protect Madoka. After Madoka's Heroic Sacrifice, Homura uses a bow that looks very similar to Madoka's.
Rei's bracelet — later given to Kira — in MARS. To Rei, it signifies his time in America, and is a good luck charm. To Kira, it signifies the beginning of her "proper" relationship with Rei.
Both played straight and subverted in Neon Genesis Evangelion by Gendo's broken glasses. Rei keeps them in her room as a sign of connection and loyalty to him. In End of Evangelion, before she ruins his plans for Instrumentality, we see the glasses lying on her bedroom floor, smashed to pieces.
The Duelist Rings (Rose Signets) are worn by all duelists. Many episodes show a sequence from Utena's childhood, when she receives hers from Prince Dios.
Juri Arisugawa's locket may be seen as this or Tragic Keepsake, depending on whether you see it as a link to the happy days Juri shared with Shiori and the Nameless Boy ( Ruka), or as a reminder of Shiori's betrayal.
In the 2001 adaptation, Albert Heinrich keeps the ring belonging to his tragically lost fiancee Hilda on a chain around his neck. Eventually, it comes in handy when he uses it while nearly completely paralyzed to shoot down Cyborg 0011.
Also, a man named Nicholas keeps a locket which is found between his clothes right after he's murdered in front of the Cyborgs. Seeing it reverses his girlfriend Lina's Laser-Guided Amnesia and breaks the Mind Control that the Big Bad of said arc had over her.
In the first episode of the anime version of Get Backers, Natsumi hires Ban and Ginji to get back a stuffed toy cat that was given to her by her mother, who is now dead.
Though Hayate doesn't know of the significance of their stone for quite a while, he's given the King's Jewel/Stone of Bonds by Mikado, it reminds Mikado of his daughter, who appears to be the original one who found the stones (she's dead and he seems to want her brought back). It's called the Stone of Bonds by MariaandNagi, and it reminds Nagi of her bond with Hayate. Eventually Mikado decides it's useful as a mark of inheritance for the Sanzenin fortune.
It's also a stone that AthenaandMidas need to reopen the doorway to the Royal Garden. Multiple uses for a single item that didn't seem particularly noteworthy at first. Oh, and there's more than one. Most notably, Wataru now has one, given to him by his mother.
One Piece: Luffy's straw hat. Some of the Straw Hats also have one. Zoro has Kuina's sword, which doubles as a Tragic Keepsake. Nami has the tangerine trees that her foster mother Bellemere used to plant. Chopper has the hat that he always wears, given to him by Dr Hiluluk, and Brook has the Tone Dial that contains the Rumbar Pirates' final song before they died.
Later on, Luffy's straw hat is revealed to have belonged to Gold Roger himself.
Goku's Four-Star-Dragon Ball. It's one of the few things he has to remember his (adoptive) grandfather by.
Asuka wears her pendant, which contains a photo of her brother who ran away from home 5 years prior to the storyline of the main series. The pendant also serves as a clue of the identity of the mysterious driver, Knight Schumacher.
Kurumada has his loupe, which was given by a man named Gen-san from his youth. With the loupe, Pei finds the cause of the understeer on Hayato's Asurada. It also helped Kurumada to find the cause of his friend Kojiro's crash on a test drive.
Pokémon: Ash received a few gifts over the series, coming from some of the friends that he's traveled with over the years only to go on their separate journeys. A handkerchief and a custom fishing lure from Misty, one-half of a Contest Ribbon and a Teddiursa carving from May, and a broken Pokeball from Gary. Brock also had a present to give, some cutlery, but since he went on to become the one with the currently longest travelling time with Ash, it was kinda moot, and these silver were never heard from again. Dawn, meanwhile, has a Ribbon she received from her mother as a good luck charm.
Barnaby from Tiger & Bunny has a burnt sash that he acquired when Kotetsu risked his life to protect him from Lunatic's firebolts. Supplimental materials say that he keeps it in his company locker as a good luck charm. Karina also has a memento from Kotetsu — a towel he got her to replace the one he accidentally ruined.
Rurouni Kenshin - the hairpin Tomoe got as a betrothal gift from the man Kenshin killed. When Oibore is seen with it, it cements his identity as Tomoe's father.
Orihimie's hairpins in Bleach were gifts from her brother who died the same day he gave them to her. She had hated them for being too childish, but after his death always wore them. They first become relevant when her brother, after becoming a Hollow, realizes on seeing the pins that she has never stopped thinking about him. They later become the focus of her spiritual powers.
Madoka’s ribbons in the Puella Magi Madoka Magica fanfic To The Stars, which have never worn after hundreds of years, one of which Homura has and the other which she gave to Kyouko. The latter resides in the Cult of Hope’s main base, open to all magical girls to see. The ribbon is also said to give visions of the future and a glimpse of the Goddess herself.
Iron Man features his prototype Arc Reactor (originally used to power a medical device keeping his heart healthy) which he wanted to throw away, but his assistant instead puts it in a cute little case, as "Proof that Tony Stark Has A Heart". Comes in damn handy when his more advanced version gets stolen.
From the Star Wars prequel trilogy, the japor snippet Anakin gave to Padmé.
The Spirit movie features this, with the locket given to Sand Saref.
The eponymous character of Hancock woke up in a hospital with no memories and no possessions except some gum and two movie tickets quite some time before the start of the movie. He treasures these items, as they're his only connection to the past he can't remember.
Cobb in Inception uses a top as a totem, which used to be the totem of his dead wife Mal.
The pinwheel that Fisher finds in his father's safe in the lowest level of the dream.
The locket that belonged to Joe's mother in Super 8.
The compass containing a picture of Peggy Carter in Captain America: The First Avenger, which plays a role in two scenes. First, the compass is seen during a film of one of Steve's missions, and acts as proof that Steve still has feelings for Peggy*
Prior to that, Peggy was annoyed with Steve seemingly flirting with a female secretary.
. Finally, Steve takes it aboard the Red Skull's plane and keeps it at his side when he attempts to bring the plane down to save millions of lives.
In Popeye, the titular character carries an empty picture frame with the words "ME POPPA" painted on the empty backing. He kisses it goodnight every night. His father also has a similar empty frame with the words "ME SON"
The mansion Manderly, in Daphne de Maurier's Rebecca, fits this — it alternates between being the main character's haven and being a grim shrine to the dead Rebecca, giving it a dual identity as a Memento MacGuffin and a really big Artifact of Doom.
In J. R. R. Tolkien's Middle-Earth stories (The Silmarillion, The Lord of the Rings) there often appear (new or old, or ancient) gifts and heirlooms, some of them important to the plot and some not. One example is the Ring of Barahir, owned by Aragorn at the time of the LotR, which by then is the most ancient artifact known to be kept by humans, being at least over six thousand years old. It was passed through generations of Númenorean kings and lords and Northern Dúnedain kings, but was originally gifted to Barahir by the elf Finrod as a symbol of friendship and loyalty for saving his life.
In Edgar Rice Burroughs's Thuvia, Maid of Mars, Carthoris finds a hair ornament, with the insignia of Thuvia's house — and unfortunately, blood. He instantly adds it to his own harness before going in search.
In Bones Of Faerie the Missouri quarter that is given to her by Caleb. It once belonged to her mother.
In Taran Wanderer, the third book of the Prydain Chronicles, Taran doesn't want to give up the sword he carries because Princess Eilonwy was the one to gird it on him.
Snidely subverted in Monstrous Regiment, in which a character's lover asked for a token of her affection, offering to have the village smith break it in half so they can each keep part of it, to re-join when he comes back from the war. She gave him a sixpence to take to the smith's, and he ran off with it and never came back.
Sayuri from Memoirs of a Geisha kept the handkerchief that the Chairman had given her when they first met when she was twelve years old. And when she became a geisha, she would carry it with her for good luck.
''But at the urgent entreaty of the princess of Khosala, who loved Bhunda Chand vainly, he gave her a lock of his long black hair as a token of remembrance.
The Peacock Parure in Aunt Dimity: Snowbound wasn't simply the family jewels of the DeClerke's, it was a reminder of the suitor Lucasta DeClerke lost in World War II—hence her deep distress when it was stolen.
In Galaxy of Fear, Tash Arranda and her mother each had a necklace with a tiny red crystal, noted to be worthless but with great sentimental value after Alderaan was destroyed. Late in the series Tash feels secure enough to wear it under her clothes and practice telekinesis on it in quiet moments.
Live Action TV
Mary's golden M on The Mary Tyler Moore Show, which represents home and stability to her. It's the first thing she unpacks in her new apartment when she moves.
The toy plane on Lost. It belonged to Kate's first love, whom she got killed during an escape from the police. Kate robbed a bank and shot her three co-conspirators to get it from a safe-deposit box.
The titular character in Bones has a small glass dolphin trinket to remind her of her father, and she gets upset when she loses an earring that belonged to her deceased mother.
The amulet that Dean always wears on Supernatural. A flashback in the third season episode "A Very Supernatural Christmas" shows that Sam originally got the amulet to give to the boys' father. When John, who has left the boys alone in a motel room again, doesn't show up for Christmas, Sam gives the amulet to Dean instead. When Dean comes back from Hell at the beginning of the fourth season, Sam (who has been wearing the amulet the whole time Dean was dead) gives it back to him. While the amulet seems to do nothing but serve as a symbol of the brothers' close relationship, in the fifth season it is revealed that it burns hot in the presence of God, and thus can be used to find Him.
Until "The Dark Side Of The Moon", of course. Castiel loses his faith completely when he finds out that God is watching but doesn't plan on helping and so gives it back to Dean, stating it "worthless". And Dean, so hurt by his brother's ideal heaven, throws it in the trash in front of Sam.Because this isn't a despairing show at all.
In the Japanese drama Shokojo Sera based on A Little Princess, Seira gave her father a necklace before he leaves, telling him he must keep it on at all times. For her sixteenth birthday, her father would send a similar looking necklace for her. And after he died, she lost her birthday necklace to Director Chieko and her father's necklace was returned to her as proof of his death, becoming a Tragic Keepsake.
In Kamen Rider Ryuki, Ren/Kamen Rider Knight wears a necklace with two promise rings around his neck to remind him what he's fighting for: his girlfriend Eri, who is currently in a coma.
The handkerchief in Djanet Sears' Harlem Duet (an updating of the love story from Othello, which also featured a handkerchief).
Dante and Vergil's amulets in Devil May Cry, which also serves as one of the keys to the gateway to Hell; in the original game, Dante discovers that Nelo Angelo is Vergil after he (Nelo Angelo) explodes, leaving behind Vergil's amulet.
In Kingdom Hearts, at the beginning of the first game, Kairi talks about a lucky charm she's making from seashells. Later in the game after Sora rescues her from Hollow Bastion, she gives the finished charm to Sora as a memento. However, the Oathkeeper is a little different from your typical Memento MacGuffin in that it also has a practical purpose; it's one of Sora's best weapons throughout the series.
He also makes a promise when he gets it to give it back to her, about 3/4 of the way through the first game. At the end of Kingdom Hearts 2, when he does manage to return home despite all odds, the first thing he does is give it back.
The Clefairy doll from the Pokemon series. Your hero buys a doll in generation one and gives it to Copycat in exchange for some random TM. The next generation, three years later, has her freak when she can't find her special doll, so you have to go find it.
The Memento Ring in Final Fantasy VI is the source of many Epileptic Trees. It's described as a memento of Relm's family. So naturally, Relm can equip it. Except Shadow can too. Other in-game cutscenes make it pretty clear that, yes, Shadow is Relm's father... so why the hell can Gogo equip it?
Perhaps s/he mimics being a member of Relm's family? Or maybe s/he's some long-lost relative?
The pendant from Chrono Trigger goes through several stages as a memento, aside from literally being a MacGuffin. At first it's just a family heirloom belonging to Marle, but Crono holds onto it after she disappears and continues to do so when she's rescued. Later, after Crono's (temporary) death, Marle takes it back as a memento from Crono. Interestingly, Magus never seems to think of it as its original status as a memento of Schala.
In The Longest Journey, April receives a stopped watch from Brian Westhouse, who claims to have received it from the Cool Old Guy Cortez and that it represents "Cortez's heart". After she rewinds it, it helps her get back to her world. Much later, when it seems like Cortez dies, the watch stops again.
Link gets a fishing pole very early in The Legend Of Zelda Twilight Princess. It seems like it's nothing more than a gesture of affection from Colin, whom he treats like his adopted little brother, but it comes in handy more than once during the plot. It can even be used to distract the Big Bad during the final battle, in keeping with Zelda tradition.
In Persona 3 and Persona 4 when maxing out a social link you receive an item of some importance to the character you maxed out the link with. It's needed in order to prove to Igor that you can fuse the strongest Persona for the arcana of the link in question.
Alpha Protocol: Sis's locket is a childhood memento. If you spare her after the boss fight, she gives it to you, symbolically letting go of her childhood, which wasn't a bed of roses...
Sir Francis Drake's ring in Uncharted 3: Drake's Deception, subverted twice, the first time it's seemingly stolen, it turns out that it was a fake and Nate still has it with him. They're using it simply to lure the badguys out since they are treating it as a MacGuffin. The second time, when he actually does lose it, Nate is shown to care more about rescuing Sully than getting it back.
Final Fantasy Tactics: The "reed flute" is more of a skill (the ability to turn a leaf or blade of grass into an instrument) than an actual momento, but it's something that binds Ramza and Delita both to each other and happier days. (Ramza also bonds with Princess Ovelia when she reveals that Alma had taught it to her.)
A picture taken in the final route of Duel Savior Destiny that shows the bonds between the main cast becomes an extremely helpful tool for everyone that allows them to surpass their former limits through The Power of Friendship.
In Resident Evil 2, Sherry Birkin carries a locket with a photo of her and her parents. Behind the photo is a vial of the G-Virus, which the Umbrella Corporation has by this time killed a city trying to obtain.
When Shiki returns to the Tohno mansion in Tsukihime he brings a white ribbon with him that was given to him by a girl he knew when he was leaving. Bad things happen when Shiki falls for the Twin Switch and gives it to Hisui instead of Kohaku.
Archer's pendant in Fate/stay night. It's the same one that Tohsaka left on Shirou when she saved his life. He carried it with him his entire life and through death, where it was used as a catalyst symbolizing her that drew Archer to her as her Servant. Also, it's the final proof to Tohsaka's suspicion that Archer and Shirou are the same person from different points in time. He gives it back to her early in the story and Shirou uncovers it, but does not realize its significance.
Also Sakura's hair ribbon, which was actually the first ribbon ever made by Rin, which she had given to Sakura before her adoption by the Matou family. It is the only real sign of their true feelings for each other (Sakura describes it as only one of two gifts she has ever received from people who are important to her, and after Rin finally realises that she can't kill her sister, she comments that she is glad Sakura had always worn it).
Antimony from Gunnerkrigg Court has a pendant of the alchemicalsymbol for antimony on a necklace, and a photo of her parents as children. Both have prompted revelations about characters: Reynardine spoke his only unambiguously sincere line upon seeing the necklace, and Annie only has the photo because she stole it.
Ron's titanium-reinforced belt in Kim Possible helped Kim remember that they were dating in "Clean Slate".
The treestar in The Land Before Time is Littlefoot's memento of his mother. It gets crushed by Sharptooth when he attacks.
The Phoenix Gate (A small, metal plate decorated with the image of a phoenix) from Gargoyles was split between Goliath and Demona as a token of the love they shared at the time. When the halves are joined, it creates a time traveling device.
Marceline's most treasured possession-her stuffed toy, Hambo. From Adventure Time Given to her by Simon Petrikov, AKA Ice King, and a tangible reminder of when he became her guardian as a girl. Naturally, she is furious when her boyfriend trades it for a new wand.