The Tokyo Mew Mew girls have a habit of using these. Mew Lettuce, the worst offender, has a pair of castanets, though at least she shoots water from them. Mew Pudding has tambourines can that rend the earth and encase a target in jello, and Mew Ichigo has a pink heart-shaped bell that shoots out waves of sparkly healing power (the remaining two team members, Mew Mint and Mew Zakuro, use the more reasonable bow-and-arrow and whip, respectively).
Cure Lemonade from Yes! Precure 5 also uses castanets, which is odd, because her teammate, Cure Mint, is an expy of Mew Lettuce.
The paopei of Houshin Engi are artifacts of incredible magical power, so they come in all sizes and shapes.
Several anime have characters who use yo-yos as weapons; while this is not as implausible as it sounds (according to popular legend, yo-yos were in fact weapons originally), it nonetheless stretches things when they have explosive yo-yos, which can go off several times without being destroyed themselves... Probably the most spectacular example of this weapon is the Robot Romance classic Combattler V, a friggin' GIANT ROBOT that wields yo-yos with blades that slice enemies like a rotary saw.
Yo-yos are just the beginning. If you're a sukeban, you've got to have a "signature" weapon. Examples include bicycle chains, cup-and-ball toys, bamboo umbrellas, guitar picks (shuriken style), billiard balls, and even a bowling ball carried by one really enormous schoolgirl.
Read or Die. Some people use paper fans. And then there's Yomiko Readman, who uses just plain paper.
There are a number of characters in the various Read or Die/Dream canons who can use paper as weapons called Paper Masters. There's also a character in the Read or Die manga who wields giant matches. And later on another character wields a giant protractor.
Nicholas D. Wolfwood, the secondary hero in the Anime/Manga Trigun could be seen as the king of the unusual weapons. He, a gun-toting, hard-drinking (apparently Catholic) priest, uses a cross called "The Punisher" as his signature weapon. A cross six feet tall, three feet wide and made of steel. The common version of the cross has one of the "arms" housing six automatic pistols on a rack, the "foot" housing a machine gun that would fit on a helicopter, the other "arm" holding ammo for this gun, and the "head" holding a recoilless anti-tank missile launcher. It's heavy because "it's full of mercy (alternately, God's love)". Yeah, right.
Nicholas's teacher and Gung-Ho Guns mentor, Chapel the Evergreen, also wields a cross/weapon (which fans call "Neo-Punisher"). His splits into twin miniguns.
Midvalley the Hornfreak will jazz you to death with his killer saxophone.
A handful of gun-based weapons really make no sense.
The minor villain Cho from Rurouni Kenshin has a whole collection of strange swords, including one that is several feet long and so thin it can be waved around like some sort of razor-sharp ribbon (this is an actual type of weapon, called Urumi).
Cho shows that Improbable Weapon Users aren't instantly badass, though, as almost every strange weapon he pulls out is effortlessly beaten by Kenshin (only the Urumi poses any threat.)
Kenshin's own sword is mildly odd, in that the sharp part is on the opposite side of the blade to enforce Kenshin's Thou Shalt Not Kill rule, meaning he's pretty much just whacking people with a blunt piece of steel.
One of Berserker's Noble Phantasms in Fate/Zero allows him to pick up anything and turn it into a Noble Phantasm-rank weapon. This includes random columns of concrete and other Servants' Noble Phantasms, at one point Dual Wielding a spear and an axe. Once he even "wielded" an F-15J. When the jet crashed, he ripped off the entire M61 Vulcan unit and fired it from the hip. In mid-air. Finally, he went Guns Akimbo with a pair of MP5K's. In fact, when he finally took out his 'true' Noble Phantasm, it turned out to be a sword - the least outlandish weapon he ever used.
Haruko, Naota and Atomsk from FLCL all utilize electric basses (and a guitar) to great effect. Electric guitars are apparently the weapon of choice for extraterrestrials. They're also used as baseball bats.
Panther Claw head Hiromi Tanaka from Cutie Honey The Live, in addition to having a stomach that can shoot missiles, uses frozen seafood as a weapon of choice. I swear!
Some of the Exorcists in D.Gray-Man have Innocences that are shaped like ordinary weapons, like a katana or a hammer, but most of them are very strange. We've seen characters with acupuncture needles, pendulums, soccer balls, and what looks like harp strings.
Violinist of Hameln has most of the characters fighting with musical instruments. The main character uses (guess what) a gigantic violin, his friend Raiel plays a solid-gold grand piano, and his sister Sizer wields a Sinister Scythe with a flute imbedded in the handle (though to be fair she actually makes more use of the scythe part; her flute is mostly used to summon the Valkyries). Of course, the results are pretty awesome, but still.
More amusingly, the series protagonist (Hamel) has been known to throw Flute (and his other allies) at enemies as a form of attack.
He also occasionally throws his instrument, though this rarely turns out well.
Heck, the original manga could be counted on to demonstrate this at least once a volume for the first seven or so, with various levels of realism, as it tended to cross over with "improbable objects used in improvised games." Notable improbable weapons include a can of specialty spray paint, which Yuugi used to draw a maze on asphalt while dodging someone which he then set on fire to incapacitate his opponent.
In Yu-Gi-Oh! GX, Amon and Ekou both use explosive cards whose effect read as instructions on how to detonate it.
GaoGaiGar's "Driver" weapon series (Dividing, Gatling and Bolting) are apparently giant, space-warping hardware tools. Meanwhile, HyoRyu, EnRyu, and their combined form ChouRyuJin use the ladder and crane of their alt-modes as giant tonfas. FuuRyu and GekiRyuJin fire energy missiles from the churner of a cement mixer. Big Volfogg uses a motorcycle's exhaust pipes as a machine gun. And then there's Mic Sounders...
Speaking of HyoRyu and EnRyu, they also have the Pencil Launchers, and ChoRyuJin can use the Eraser Head. They are as silly as they sound.
And of course, The Captain Koutarou Taiga's preferred weapon is consistently a golf club. Even when he puts on his ID Suit. He even calls the attack.
TITANIUM HEAD DRIVER!!!
Get Backers. Perfume, mirror fragments, thread, needles, and cloth seem to be the worst offenders. The "poison perfume" is justified by some kind of magic, but... thread. In practice, it's pretty Badass (at least in the manga), but...
In the manga they were not threads but harp wires. Slightly more believable as weapons, but still unique.
Busou Renkin has plenty of these. Exploding fun balls, Tokiko's leg-blades, and many more.
Many of the characters in Blade of the Immortal use weapons that look incredibly cool... until you start asking questions about how they'd work in reality. The creator, Hiroaki Samura, hung a lampshade on this with the "Samura's Weapon Shop!" feature, which explains all the weapons, including the ones that don't make any sense. Examples: two sickles connected by an expansible chain ("The chain fits into one of the scabbards, and can stretch out to about seven feet. Whether this is good for anything is another question entirely."), a blade with little curved hooks on both edges ("What the hell is this thing? Don't ask me."), and two blades so narrow they look like kitchen skewers ("To be perfectly honest, I wonder why he doesn't just use a normal sword..."). Later, the sadistic Shira, who's had one hand cut off by Manji, makes up for this by (warning: squicky) sharpening the protruding bone and using that as a weapon. It works about as well as you might expect.
Surprisingly, these examples work in real life: the chain-and-sickles is a variation of the traditional Japanese Kusari-gama, also used by Guilty Gear X's Axl(in the same two-sickle formation); the hooked blade can be justified by the additional damage caused by ripping action of the hooks upon cutting (the jagged edges of the wound heal slower), in the same fashion as soldiers who used to saw teeth into their bayonet blades; as for the narrow sword, almost all swords from the renaissance onwards were very thin, flexible blades, useful for only their stabbing action (they could only inflict superficial cuts, nothing like a medieval claymore).
Hagi's signature weapon in Blood+ is his cello case.
A cyborg assassin in Ghost in the Shell: Stand Alone Complex uses a gun implanted in her right arm that fires coins. Just how it manages to shoot rolls of coins -assuming they're not just a solid, welded-together stack thereof - in a way that would make a SPAS-12 combat shotgun green with envy is never explained. Her reasons for using them are readily apparent, though; she appears to have distinctly anti-capitalist principles, so the coin shotgun may be her idea of irony.
Pics! Unfortunately, as far as US currency is concerned, only dimes fit right in a 12 ga. and they are too light to do much damage at range. But it works! in theory.
To be fair, it was most likely a railgun of sorts. Even the Major was confused by it.
Katekyo Hitman Reborn!. First there's Joshima Ken, who uses different sets of teeth to adopt the abilities of different animals. Kakimoto Chikusa who uses yo-yos that shoot out poisoned needles. M.M who uses a clarinet that, when played, creates special sound waves that cause the substance the clarinet is aimed at to boil instantly, which is called 'Burning Vibrato'. Levi who uses umbrellas that discharge electricity. Bianchi who specializes in poison cooking. I-Pin who enhances her martial arts skills with special gyoza dumplings laced with garlic, which numbs the brain and forces the victim's muscles to involuntarily move on their own.
Tsuna's woolly mittens. Hibari's handcuffs . Gamma's pool cues, Lancia's giant flail which can utilize air currents to inflict more damage as well, Shamal uses mosquitoes, Kikyou killed Genkishi using freaking flowers, Lambo's electric cow horns, Suzuki Adelheid's metal fans, Vongola IV's fork. Amano really has a thing for unusual weapons. Most recent is Daemon Spade's playing cards, which are faithful to the name of their user and able to make mind raping illusions.
If you don't think a blanket woven out of the strongest metal in the world, or being able to use your blood as a weapon is improbable, then you've got no idea. Black Cat indeed features some improbable weapons.
Metal Armor Dragonar features one of the strangest sniper weapons in any Real Robot anime series: The Caulking Gun. To elaborate, it fires a shell that penetrates Humongous Mecha armor, then proceeds to inject a fast-hardening foam substance that damages computer systems, destroys circuit conductivity, and for the very unluckiest of victims, suffocates the pilots by filling the cockpit. Particularly effective since every robot in the series can fly, and is usually doing so.
Dr. Black Jack has been known to use scalpels as weapons.
Outlaw Star has Grappler ships (including the ship of the title). Ships with arms. That tend to use giant, EVA-style knives. And similar melee weapons, including axes. And oversized handguns. And Twilight Suzuka, who is a master of the bokken that would make Tatewaki Kuno green with envy. Not only is her bokken the weapon she dispatches her quarry with, but she is so skilled with it that she can smash massive craters in solid stone and steel from a distance with a single swipe of her sword (using this on the roof to escape in her debut episode) and cut a bus cleanly in half with a single vertical swipe.
Ranma ˝, as the anime that gave us Martial Arts and Crafts, naturally has an equally bizarre and improbable array of weapons for martial artists to use.
In the main characters alone, Kodachi (gymnastics ribbon) and Happosai (pipe), Mousse (who throws everything bar the kitchen sink), Ryoga (bandannas as projectile weapons) and Shampoo (chui with oversized heads, they're like basketballs on short staves). Ukyo (high speed cooking and batter as liquid cement, as well as a sort of spatula thing.
The oddest weapons, however, tend to be seen by the minor characters- and the anime outdoes the manga in this regard. There's Sotatsu Jikei'ien, who wields ink, paper, and a calligraphy brush the size of a man, Tamari Kaminarimon, who uses tops, hacky-sacks, thread and a kendama as weapons, and can presumably also use playing cards and marbles like her fellows do? Prince Kirin uses chopsticks and rice.
One Piece should be a chief offender of this trope, as characters have used spinning tops, perfume, a saxophone, balloons, paint, ramen, and even clouds. And let's not even get into some of the weapons the characters make with their Devil Fruits.
Covering opponents in soap. Exploding boogers. Cola farts. Actual ropes tied into knots, plus knives tied into some of the ropes. Flippin' tears turned into whale projectiles.
Many of the O-Parts in 666 Satan qualify, especially Futomomotaro's Mackerel Sword which is even weirder than it sounds: it's a rigged mackerel with a hook for a handle that can release methane gas.
In Ashita no Nadja, Sylvie uses a parasol as a sword, and Grandma Anna loves to swing her frying pan around.
Part 4's antagonist Yoshikage Kira, when in disguise as Kousaku Kawajiri, uses a new found Stand ability to weaponize Kousaku's son Hayato, turning him into a bomb trigger that kills whoever tries to investigate Kira.
Everyone in Hunter × Hunter. To name a few, there's bank interest, gum, a dart board, a vacuum cleaner, a giant pipe and a fishing rod (used by the main character, no less). All of which are put to serious good use, like fighting giant ants bent on world domination.
It goes both ways: The aforementioned dartboard is a weapon of one of the ants. Other weapons that don't have their own tropes include a cell phone, fleas shot from a sniper rifle, a book (its text, not as a blunt object), needles, teleporting gorillas, a volleyball, one's own detached fingertips, a tiny floating birdcage, a surfboard, planet Jupiter, explosive mosquitoes, a slot machine staff, and an entire savannah the user can transport to the immediate area.
Rozen Maiden much? Okay, they're dolls, but still, Souseiseki charges at people armed with a pair of giant scissors, and when forced into melee Suiseiseki whacks people with a watering can.
One Quirky Miniboss Squad from Berserk uses torture tools as weapons. These include pliers used to pluck out peoples eyes, saws, some sort of grappling hook, a restraining device mounted on a long pole, and a massive wheel. Also, Ganishka's demon soldiers wield bizarre looking horn things that are used sort of like spears.
Durarara!!: Shizuo's trademake weapons are street signs and vending machines. Also, Mikado and Izaya, to a lesser extent, both get honorable mentions for harnessing the awesome power of the internet and unleashing it on their unsuspecting enemies.
Seiji. He managed to stab a PEN into Heiwajima Shizuo Who Vorona couldn't penetrate his chest more than half a centimeter with a knife and Shinra's destroyed some of his best scalpels operating on him.
In Soul Eater, Kim Diehl uses a lantern as her Weapon. The aptly named Jackie (Jacqueline Dupree) manages to combine flying broom, flamethrower, and explosive device in one improbable, manically grinning package.
Justin Law also sort-of counts as an Improbable Weapon. He is a guillotine, meaning that his Weapon form proper is fairly useless for Technicians in Shibusen's line of work. However, he gets around this by transforming parts of his body into bits of his guillotine form; blades on his forearms, for example.
And then there's the South American Death Scythe, Tezca Tlipoca, who calls himself the 'Demon Mirror'. We've no idea how he uses this to fight, however, because Medusa scarpers before he and his * monkey* Tech get a chance to attack.
69 shows that the Demon Mirror's powers involve creating reflections of people, which he uses to disrupt Justin and Medusa's fight.
In Sid's first appearance, he fought off four of the main characters using his own tombstone as a weapon.
And then there's the Arabian Death Scythe, who is...a magic lamp. Yes, like the one in Aladdin.
Vita of Magical Girl Lyrical Nanoha. Take a close look at the shape of her hammer's standard form. Now, note the balls she uses as projectiles. That's right, Vita fights using a croquet set. And yes, she did play croquet in her spare time when she was living with Hayate on earth.
Orihime uses her hairpins. The petals of the hairpins transform into six fairies that can, in different combinations, produce barriers that perform different tasks such as shielding, healing, killing and deflecting. Various characters have speculated that her powers may potentially be the most powerful in the entire story but her gentle nature holds her back from achieving that kind of potential.
Quincies possess small crosses that they wear as either bracelets, broaches or belt buckles. These crosses form the focus for their offensive ability and transform into combat weapons, often bows but they can be any weapons the quincy prefers to use.
Similarly to Quincies, Fullbringers form an emotional attachment to an object and that object becomes the basis for all their offensive power. Ginjou's weapon is a necklace, Tsukishima's weapon is a bookmark, Yukio's weapon is a video game console, Jackie's weapon is a pair of muddy boots, Giriko's weapon is a pocket watch and Shishigawara's weapon is his lucky knuckle ring. Sado joins this group when it's revealed that, to produce his arm weapons, he's actually weaponising his skin.
Master Asia from G Gundam was known for taking down Mobile Suits with sashes (pieces of cloth) and BARE HANDS. He can also take down giant robots with a silk scarf.
Mahou Sensei Negima!'s Mana uses thrownyen pieces. Not only the nature of the weapon one wonders how she keeps so many up her sleeve? Her opponent used a super-powerful cloth as her weapon.
Asuna uses a fan in serious combat until she manages to upgrade into a sword. And not a war fan, an actual paper fan, and it's not entirely played for laughs due to some special intrinsic abilities. Also, Evangeline fighting with strings (it was still awesome though) and Makie's ribbon (more so in the anime than the manga, where despite being an Ensemble Dark Horse she gets little screen time due to being very weak), which is apparently magic or something because it can do anything.
While not much of a combatant, Makie has shown an inhuman amount of skill with her rhythmic gymnastics ribbon, using for such things as crossing pits in Library IslandIndiana Jones style, as well as being able to pick up and throw people.
All that skill with it and she still only got 4th place in a gymnastics Competition....
During the Tournament Arc, Setsuna uses a deck brush in lieu of her sword to get around a restriction on bladed weapons.
Don't forget Chao's most powerful and greatest attack, the greatest psychological weapon created by the powers of the future...a copy of her family tree, which she claims contains the identity of Negi's future wife. The result? "Negi party obliterated! New record: 57 seconds!"
All this is outmatched by Chachamaru's pactio artifact... a catgun. A friggin' catgun. It's actually a targetting laser for a Kill Sat. The Kill Sat is also shaped like a cat.
While Mahoujin Guru Guru's heroes keep to standard fantasy-fare like staves and magic swords when using weapons, an exception exists in JuJu. JuJu is a battle priestess of her church and carries with her a portable altar. In battle, she prays at it for her god to smite bad guys down, and He does. Taking it a bit further, this tends to put JuJu into a power-mad trance which can be broken only by someone shaking a magic baby rattle at her.
Eclair from Kiddy Grade often creates a whip made out of her lipstick by drawing a line of lipstick on a surface then pulling it off the surface as a whip.
Bakemonogatari's Hitagi Senjogahara pulls a box-cutter blade and a stapler on Koyomi('s mouth) in the first episode. When he later catches up to her on the stairs she pulls handfuls of sharp, miscellaneous office supplies from nowhere. In the second episode she states outright that she keeps them on her person at all times for self-defense.
Russia of Axis Powers Hetalia is known for using a water spout. And it's more awesome than it sounds.
He's not the only one: China uses his wok and cooking implements, Hungary uses her frying pan and Greece uses a metal cross.
And although we have yet to see it used as a weapon, Russia's older sister Ukraine is often shown wielding a pitchfork.
White flags are weapons as well. And pasta, don't forget the pasta. Why? Because Italy says so.
Blazer Drive no stranger to this trope. The characters use stickers for practically all their attacks. Dachi, the main character, uses a gauntlet that sends out wires which he uses in conjunction with his electrical attacks. Heck one of the characters uses a hammer comprised of a giant fork and a jelly roll!
The Death Note, being a notebook that kills people whose name is written in it, could easily be used as a weapon instead of a method of execution.
It is, in fact, a serial-murder weapon and if Light had ever been brought to trial would have been treated as such. Probably.
Mugen from Samurai Champloo wears geta that have metal plates fitted to the bottom of them, which he uses to deflect sword attacks. He is also able to use them as effective blunt weapons, or can throw them with a great amount of force.
There is also the leaders of the graffiti gang, who use an oversized butterfly knife and a practice katana with nails sticking out of it.
Bobobo fights using his nose hair. When this fails, he uses his armpit hair. Not to mention one of the main enemies fights by getting eaten (he's made out of Jello). Also in Bobobo's arsenal are a Magical Girl that comes out his head, an ongoing love-drama between two squirrels that live in his Afro, not to mention cross-dressing just to make an opening in his enemies' defense.
Don Patch fights with leeks, and Bobopatchjiggler fights with a sword that has a stone head on the edge, making it, for all intents and purposes, blunt.
In the Chibi Wrap PartyOVA for the original Fullmetal Alchemist anime, Scar pulls off his scar and throws it like a shuriken. Automail and alchemy also apply, such as a girl who can fire a deer slug from her kneecap, or using blood, giant statues of a muscular bald man, or (in the games) a Paper Fan of Doom as ammunition or defensive/melee objects.
Roy Mustang himself could be said to fit in with this, snapping his fingers creating a massive explosion.
Ed has been known to hit people with his own detached prosthetic arm.
Basquash!, which could be called "Weaponized Basketballs: The Animation." Main character Dan escapes a gladiatorial pit fight by turning down swords, spears, and flails in favor of a ball and his trademark Lightning Ball shot.
Sailor Neptune of Sailor Moon uses a Mirror, the Deep Aqua Mirror, as her weapon, though not as a physical one. Pluto uses a staff, the Garnet Rod, shaped like a key which holds her real magical weapon, the Garnet Orb, at the top. After their Super Upgrades Jupiter gets Oak Leaves and Mercury gets a lyre.
Surely Tuxedo Mask throwing roses deserves a mention. Even if his roses seem to be magically sharp, with greater aerodynamics, range and accuracy than a well made dart, and notwithstanding their other powers (for example, they measure his alignment when he's Brain Washed And Crazy in the first season). He also uses a cane that can function as anything from a sword, to a bo, to a throwing weapon itself.
Tiaras are not adequate projectile weapons. Their effectiveness in the show (and the effectiveness of all the weapons mentioned above), is an indication of how the writers themselves invoke this trope in choosing weapons for the characters.
More like an improbable shield, but in the BW arc, a Scraggy and a Scrafty pull up their "pants" high enough to protect themselves from an incoming Ember attack.
Megumi from Muteki Kanban Musume learned how to throw blackboard chalk with high precision, after she witnessed how her teacher managed to hit Miki with a piece. Later she switches to hot dog skewers, since they are easier to order for her bakery—and of course much deadlier.
Sebastian in Black Butler, being a butler, chooses to fight with silverware.
Gintama. Where to start? Gin uses a wooden sword as effectively (if not more so) as everyone else uses their katana, and on occasion has had it modified to squirt soy sauce. Kagura uses her umbrella (which also doubles as a machine gun). In several episodes, Hijikata uses a giant mayonnaise cannon (in one episode taking out a helicopter). Bansai carries a shamisen and uses the strings to tie up opponents. The second half of episode 99 also has several characters wielding people as weapons.
In Jackals, Nichol's weapon of choice is, er... well, completely fictional in design, resembling nothing so much as a grossly oversized bat'leth. He calls it "the Alligator", because of its jagged "teeth", colossal size, and ability to rip through human flesh like it ain't no thang. Albert "The Giant" Gacho gets a little more extreme when he faces off against Nichol by tearing a lamp post right out of the ground and using it as a weapon. Gacho's friend Hans favors exploding fake roses, if you can believe it. There's also Turis, who has a strange mechanical spider on a "web" line, almost functioning like a rope dart but with several unique properties.
Sora of Change123 fights with a sharpened set of house keys on an extremely long key chain.
magico is a manga that features a mage that use a broomstick. You know what he once did with this broomstick? He destroyed an island-sized castle .
Sanae uses her very long, which end in improvised bolas, as her weapons (although not very effectively).
Touka uses a ladle, which she can use both as a melee weapon and a projectile.
Multiple characters in Anpanman. Some examples include the Donburiman Trio (Tendonman uses chopsticks, Kamameshidon uses rice paddes, and all three can throw their lids), Tekkanomaki-chan and Komaki-chan (both use bamboo sushi mats rolled up like a bo staff), Yakisobapanman (double metal spatulas), Chawanmushimaro (launches out ginko nuts and whacks them with his fan), Daikon Yakusha (daikon radish rapidly fired using a hand grater), and Datemakiman and Sakuramochi-nesan (both use bangasas as striking weapons, Sakuramochi-nesan also uses mochi as a trap for enemies).
In Puella Magi Madoka Magica, Homura Akemi used a 1-wood (yes, the golf club) as her go-to weapon in her early days as a Puella Magi.
This trope seems to be the mark of childish or inexperienced magical girls. Nagisa, of Rebellion fame, uses a bubble-shootingtrumpet, while Kazumi isn't above bludgeoning her opponents with her gigantic laser cross. According to Word of God, Mami herself didn't figure out how to create her signature muskets until later in her career, and spent her early days fighting witches with nothing but ribbons.
Mahiro Yasaka from Haiyore! Nyarko-san uses forks; his mother Yoriko, a part-time monster-slayer, uses them better. Regardless, both of them are good enough that they've actually put the fear of...well, man into the hearts of the three Cthulhu Mythos deities who live in their house.
Miyu from Vampire Princess Miyu use a hair ribbon as weapon. And it is far more lethal than you could ever imagine.
Kill la Kill has the obvious Ryuko, who uses half of a giant pair of scissors like a cutlass. The Student Club Presidents all use weapons relating to their profession, which often leads to this; Omoiko's giant tennis racket, for example.