The puppets used by Sand ninja in Naruto are gigantic Swiss Army Weapons, being, well, a huge collection and weapons and tricks gathered up into the shape of a human or animal puppet. Sometimes, the puppets even have combo attacks.
As the name suggests, the Ten Commandments sword of Haru Glory from Rave Master has ten forms. These include a sword that increases the speed of the user, a form that splits it into a fire sword and an ice sword, and another that can sever pure energy such as magic but passes through solid objects. There's also Musica, whose abilities allow him to change the silver necklace he wears into any weapon, usually a spear or shield.
The Kogan Anki of Kaoru Koganei from Flame of Recca can take turn into a swallow, a chain and sickle, a boomerang, a pair of giant scissors, and a bow, as well as a sixth secret form. The transforming process is complicated though, and only someone as adept at puzzles as Kaoru can change it from one form to another while in the heat of battle.
The Zanpakutou (Soul-Cutting swords) in Bleach usually change in appearance when in released form, be it from one type of sword to another (like Ichigo's Zangetsu, which goes from a giant khyber knife to a classy black daito), one type of weapon to another (Ikkaku's Houzukimaru from katana to hybrid naginata and three-section staff) or single-to-double weapons (both Shunsui and Ukitake's swords).
Some of them have different shikai (initial release) and bankai (final release) forms apart from their sealed state. Byakuya, for example, has a running total of 4 different forms of bankai.
Note, however, that this is technically more of a Super Mode than a Swiss Army Weapon, especially in the case of Bankai. Even though the altered functionality of the weapon is often part of the point (especially in many early examples of Shikai), the main reason to use it tends to be a general increase in power and the acquisition of new abilities.
In the UC and CE productions, many of the later mobile suits' shields have integrated beam or projectile launchers.
The Zeta Gundam had both its beam rifle andBFG double as beam sabers, while the Double Zeta Gundam had two beam cannons whose barrels could also become giant beam sabers.
In V Gundam, a rotating beam saber functions as weapon, shield, and helicopter rotor.
In Gundam X, the titular Gundam's rifle is its shield. Later, when it's rebuilt into the Gundam X Divider, it loses the rifle-shield combo for a double barreled beam machinegun and the Divider Shield, which is a shield, a 19-barrel beam-firing BFGand a booster pack!
In Gundam SEED, the Blitz Gundam's right arm mounts the "Trikeros offense/defense system", which is a shield that also contains a beam rifle, a metal stake launcher, and a beam saber. Its MSV-based mass produced variant, the N Dagger N, pairs it down to just the shield and beam rifle.
It is said that the Sword Strike Gundam's "Schwert Gewehr" anti-ship sword was meant to also have a beam gun built into it, but that one was a prototype, so it didn't have it. A later model, the Sword Calamity, did.
The Gundam Astray Blue Frame Second L from the Gundam SEED Astray manga has the Tactical Arms system, which is a booster backpack that can become a BFS or a gatling gun. The Sword Calamity in the same series carries a pair of BFSs that double as laser guns.
A model kit version of the Blue Frame Second L takes this even further, enabling the halves of the sword to detach and become beam blade tonfas.
The recently released Master Grade kit of the Astray Red Frame ups the ante further by giving it its own Tactical Arms, where the booster backpack can become a BFS, a longbow that fires laser beams, a V mode (not sure what its for yet), a weirdly named Delta mode (which may be related to the Stargazer's method of moving long distances without using power like a solar sail) and finally, a 'Work Mode' where the entire Tactical Arms mounts on the left arm and works like Kyrios' pincer claw while the handle detaches and becomes a beam torch; this mode however, (in a moment of Fridge Brilliance) rather than being for combat, is for making salvage work and other Junk Guild tasks easier for the Red Frame to do.
Additional moonspeak decrypting suggests that Red Frame's Tactical Arms II also carries abilities to pull Gold Frame's Energy Drain and be controllable via DRAGOON system.
In Gundam 00, both the Gundam Exia and the titular 00 Gundam have swords with built-in beam guns.
Taken Up to Eleven in Gundam Build Fighters Amazing, the Mercury Lev almost have everything, one section can switch between any of the melee weapons while the other can switch between any ranged weapons.
Nicholas' giant cross from Trigun is a portable pistol rack, a machine gun and a rocket launcher.
There's also Rei-Dei the Blade, whose sword blade can be fired from the hilt while the sheath functions as a rifle.
Genesic GaoGaiGar's multi-segmented tail can turn into at least three distinct weapons. The end of the tail (actually a bird's head) transforms into a knife, and the other three segments either form the base of the Bolting Driver or reconfigure into gloves for the Finishing Move Hell and Heaven.
Also of note is the bucket of RaiRyu Dump truck form, which in robot form serves as a shield, an electric gun, and a means of flight.
In Busou Renkin, this is standard practice - unlike in most shonen, becoming stronger isn't about reaching newpowerlevels, but about finding different and creative uses for the weapon you have. A later character, for example, has tiny homing chakrams for weapons. In addition to controlling them, he can use them to enhance his punches, ride on them like wheels, or even propel himself through the water by spinning them.
The Kero Ball from Keroro Gunsou features such devices as a taser, a disintegration ray, a teleporter, a levitation device, a duplicator, a repair module, and more. It can also reconfigure household clutter into tasteful furniture and electronics.
FLCL gives us Haruhara Haruko's flying surfboard chainsaw machine-shotgun Rickenbacker bass guitar that can open interdimensional portals in other people's heads by smashing it into said people's heads.
At last count, InuYasha's Tessaiga's sheath can generate a powerful barrier and summon the blade to itself. The sword itself can create extremely powerful anti-youki barriers, extremely dangerous blasts of kenatsu, mountain shattering blasts of air/youki, rebound and amplify youki attacks, cut through barriers (up to a point), shoot out high powered barrages of diamond spears that flat out dissolve even stronger barriers (and can be amplified by the aforementioned mountain shattering blasts), absorb youki (and ghosts, and senki, including that generated by a human), regurgitate/redirect youki, purify youki, generate flames, create portals into hell/other dimensions/the future/SPIRITUAL RESTING PLACES IN OTHER DIMENSIONS IN THE FUTURE. Did I mention that it seems to also be at least semi-sentient (hell, possibly even prescient, considering that it and its brother are able to figure out when and how to be used, even when their masters aren't even aware that they need to be used — or not used — at all), and that it eats youki, which means that it can pretty much gather powers ad infinitum?
Black★Rock Shooter's Rock Cannon and Strength's Ogre Arms both transform multiple times over the course of the 2012 anime, usually in mid-combat. It's not always effective but it's constantly impressive.
In Black Cat, Sven has such a weapon masked as an attache case.
Éclair's lipstick in Kiddy Grade can be used for just about anything you'd use another tool for and it can turn into a whip.
High School Dx D has Kiba's Sacred Gear, Sword Birth. Apart from the ability to arm himself at a moment's notice, the swords it creates can have whatever properties Kiba wishes to assign to it, as long as those properties would be physically possible. This leads to situations like his light-nullifying sword being broken, only for him to instantly draw one that repels darkness instead. When later events reveal the Magic A Is Magic A of the setting is starting to decay, he starts using it to materialize Holy-Demonic swords, which are impossible to create, but there's no longer a natural law saying they can't exist.
With a little boost from Boost from Issei's Amplifier Artifact, Sword Birth also becomes a useful area-of-effect weapon, allowing Kiba to sprout a Field of Blades and skewer anyone unfortunate enough to be caught in it.
Minor Spider-Man foe Mr. Stone has "multi-cannons" that fire explosives, blinding flares, burning flares, sticky immobilizing goop, stun-pods, and more.
Likewise, Spidey's clone, the Scarlet Spider, had "webshooters" which were bracer-sized devices that could use Spidey's traditional web fluid in a variety of ways. His favorite (besides the standard strands) was "impact webbing", a small ball that would explode into a gooey mess on impact.
And Spidey himself could do that in some video games.
His response to a female colleague asking if he could impregnate her from across the room? "I am full of useful devices."
Image Comics' cybernetic hero "Superpatriot" has arms that work this way. They go "clickclackclickclack" for a bit, as they become any sort, or number, of weapons (usually projectile weapons) he needs.
Judge Dredd has the Lawgiver pistol, with ammunition that can configure itself to the operator's specifications including Armor Piercing, Heat Seeking, and High Explosive as a sample.
Which leads to the epic scene where Dredd pulls the trigger on the Big Bad, only for the gun to inform him "lethal rounds exhausted". So he yells "signal flare!" and fires again.
Avengers: The Initiative introduced the Tactigon, an alien symbiotic weapon which attached to the wielder's arm and became anything that it needed to be, whether that was an energy axe, razor wire, an energy blaster, or even a device for removing other alien symbiotic weapons.
In Final Crisis Aftermath: Run, General Immortus' team of losers includes Miss Army Knife, the Woman of a Thousand Attachments, who is a Swiss Army Weapon.
The Blue Beetle's scarab. When it bonded to Jaime Reyes, the latest Blue Beetle, it gave him alien armor that can sprout energy weapons out of his forearms, or turn his entire arms from the elbows down into energy weapons if he needs something of a higher caliber. Also saw blades, gripping claws, and smaller extra arms when he needs to grasp more than two things at a time. He can fly by wings, by a rocket mounted on his back, or, in a heavy storm, by a surfboard attached to his feet.
Death's Head has several different weapons that he can swap his right hand with. His most common ones are a mace, an axe, a blaster, and several different types of missiles.
DC's 1958 space hero Rick Starr Space Ranger (no relation to Isaac Asimov's 1952 David Starr, Space Ranger) uses a "multi-raygun" that can fire an anti-gravity ray, bubble ray (imprisons the target in a forcefield bubble), dissolverizer ray, explosi-discs (energy grenades), paralysis ray, thermoblaze ray and anything else that a given plot might need.
In Topps Zorro comic, Lucien Machete had a Hook Hand had a number of attachments that allowed him to convert it into different weapons, including spring loaded blades that could be fired at an enemy.
The Metabarons had the Multi-Cogan. According to the RPG expansion of the comic, the regular Cogan was a rifle that shot "lazed plasma bolts" (maybe plasma riding on a laser beam?). The Multi-Cogan took that and added a heavier charge, plus an integrated grenade launcher and vibro-bayonet.
A Growing Affection has Kitsune, Naruto's staff-blade (a fancier club), that can turn into a broadsword, a BFS, a chainsaw like Rasengan sword, and a shield. It also resists heat and electricity, giving it more mundane uses.
Hinata's bracers Ginmaki almost qualify, they have a variety of tricks, but only two 'forms', their regular form and a broader forearm blade.
In Kyon Big Damn Hero, Kyon has three, Hakurouken, his beam saber that cuts metal but only stuns flesh and also is a full featured sonic screwdriver. Altair and Vega are his guns that take on multiple forms, like a sonic cannon, realistic stun gun, emp, and wire cutters. In addition, all three combine to form a Kill Sat.
Not to forget the autodestruct/demolition charge function not mentioned above... "I don't like warriors. [...] Now a real killer, when he picked up the ZF-1, would have immediately asked about the little red button on the bottom of the gun."
The autotracking function was the likely inspiration for Resistance's Bullseye Rifle.
The Shaw Brothers feature Jade Tiger was arguably the king of this trope. The villainous Four had a sword that had two smaller swords inside of it, and the last one was also a bomb. The movie's hero had a staff that could be turned into a spear or gigantic nunchucks. At the beginning of the film a blind monk takes out his glass eyes and throws them as grenades.
In Beverly Hills Cop III, Serge's "Survival Boutique" sells a combination minigun, microwave oven, rocket launcher, portable TV, flamethrower, beverage cooler...
As in Comic Books above, the Lawgiver handguns from Judge Dredd can switch to several types of ammunition with a simple voice command and without needing to change magazines. Like in the above example, this leads to the even more epic scene where the Big Bad pulls the trigger on Dredd, only for the gun to inform him "lethal rounds exhausted". So Dredd wrestles the weapon from him, yells "signal flare!" and returns fire.
The movie Where Eagles Dare has "Swiss Army Dynamite". Can be triggered by either timer or tripwire, it's used for everything from traps to the wholesale demolition of bridges and buildings. And they use so much of it in the movie that 90% of the equipment in their packs has to have been these.
The Roy Orbison movie The Fastest Guitar Alive included a guitar that played perfectly... and shot bullets. While that is only two functions in comparison to the dozens that other devices in this list show, the sheer impossibility of a single device that both fires bullets accurately (without a trigger mechanism) AND does not need any more tuning that a normal guitar qualifies.
In Our Man Flint, superspy Derek Flint uses a cigarette lighter of his own design which can perform dozens of functions, including lighting cigarettes.
Quite a number of James Bond films have Bond getting a Swiss Army Watch. In addition to telling time, they also have various other functions depending on the movie. Some of these functions include a built in detonator, grappling hook, and laser.
Just his watch? Don't forget his cell phone that also had a tazer, a lockpick, and a fingerprint reader/viewer, plus was able to control his car. And what about the keychain that had lockpicks, stun gas, and plastic explosive? And the mother of all James Bond Swiss Army Weapons: the From Russia With Love attache case, containing a sniper rifle, ammo, knife, gold coins for bribing, a spare gun, and a teargas bomb booby trap.
Arguably all of 007's gadget cars are Swiss Army Weapons, since they are fully-functional cars yet also contain machine guns, ejector seat, rockets, jet motors, lasers, and one very special car turned into a fully-functional submarine!.
The Naked Gun parodies this with a simple pistol with so many add-ons that it eventually becomes a full-sized howitzer.
Don't forget the SWISS ARMY SHOE!
In Hot Shots! Part Deux, the main character has an impressive looking knife which has built-in chainsaw, wire-cutter, and drinking straw.
In First Blood and Rambo: First Blood, Part II, Rambo's knife has a variety of additional functions. In the weapons department, he can tie it to a stick (there are holes in the hilt to thread the cord through) and make a spear. It also has a compass, thread and needle for stitches, fishing hooks for fishing, waterproof matches and two screwdrivers (which form the hilt).
xXx achieves the same effect with a fairly conventional .44 revolver and various kinds of Abnormal Ammo.
From the Star Wars Expanded Universe novels featuring the Yuuzhan Vong, hails the amphistaff. A serpentine living weapon that can be used as a whip, a sword, a staff, a spear, and can even spit poison/acid.
Jacen Solo (who has a Force specialty of talking to animals) was able to wear fifteen or so amphistaffs around him as a suit of armor, swapping them in and out so that they can rest and he can use new ones.
In Rick Riordan's The Heroes of Olympus Jason's weapon begins as a gold coin; a toss causes it to become an Imperial Gold sword or javelin on heads or tails respectively.
The "soft weapon" from Larry Niven's short story "The Soft Weapon" is a spy weapon from the defunct Slaver Empire. It's a communicator, laser, energy-absorber, ballistic weapon, monosword, and has a total conversion setting. It's also a little too smart.
Also from Pratchett the Discworld has the Lancre Army Knife, which contained such functions as The Device for Locating Small Grains of Hope. Fortunately, it also had The Device for Ending Arguments Very Quickly, possibly a knife but which, given the features suggested by King Verence, could have been anything capable of causing someone to bleed when stabbed with it.
The FORCE: Ground multi-rifle from Dan Simmons's Hyperion Cantos has multiple modes, including a high powered particle beam, pulse bolts, a killing laser, a standard rifle, heat-seeking flechettes, smart grenades, and a targeting system that meant you would never miss, in a sandstorm, at ten kilometers. According to the book, it could do just about anything besides cook your dinner, and in the field, soldiers would often use the laser on a low setting to do exactly that.
While more of a weapon system than a weapon, the Mobile Infantry's powered armor from Robert Heinlein's Starship Troopers probably applies. The narrator describes his suit as coming with a flamethrower with multiple settings, a rocket launcher with multiple forms of warhead (including peewee nukes), a wide variety of high-explosive bombs/grenades, and presumably some sort of standard bullet-firing weapon, though he never explicitly uses one at all during the same mission. Not to mention that little experimental toy. "I'm a thirty-second bomb! I'm a thirty-second bomb! Twenty-nine!... Twenty-eight!..."
The Panacea rifle from Seekers of Truth. The polymer barrel can expand and contract to change its interior diameter. If you find some ammo lying around, and it's no bigger around than 40 mm, go ahead and shove it in there. Also features a flamethrower, a high-pressure water cannon, and an electronic scope with built-in bullet drop compensation. Doesn't have guided missiles or anything, because that would be silly.
The second generation of the rifle is a pair of gauntlets with guns on them, which can fire anything 20 mm or less.
Dan Abnett's Triumff has a literal Swiss Army Weapon - the series is an Anachronism Stew of steampunk, modern fantasy and Victorian themes. The main character's main weapon is the couteau suisse, a hex-powered weapon which, at the touch of a (somewhat unreliable) button, will manifest a variety of fighting blades (usually a rapier, but on one occasion, a cutlass), as well as, when the mood takes it, traditional Swiss Army Knife tools, including a veg peeler.
Prince Charming (yes, that's really his name) in John Moore's Slay and Rescue receives as a gift a sword with a number of tools folded into the grip. It didn't come with a manual, though, so Charming and everyone else who admires the device is puzzled by one particular fitting. Fortunately, Charming figures out when it's most needed that the mystery tool is a lockpick.
Old Man's War by John Scalzi. The nanotech-based weapons used by the main character can do anything from rockets, grenades, and bullets, and fire them in whatever pattern needed thanks to the Brain Pal interface.
Similar to the guns in Old Man's War, Jeffrey Thomas's novel Blue War had the Assault Engine. Assault Engines are a combination shotgun, carbine, grenade launcher and energy beam projector to deal with any threat in the jungles of an other dimensional Vietnam-expy.
The artifact without an instruction manual in the choose-your-own-adventure book The Citadel of Chaos. It's about as likely to turn into a squeaky hammer and a sunsword.
In The Hitchhikers Guide To The Galaxy, a towel is dubbed the most important tool for any galactic hitchhiker. It can be wetted down for hand-to-hand combat, made into a blanket, coat, or sail, used to avoid the gaze of the Ravenous Bugblatter Beast of Trall... and of course dry yourself off with it if it's clean enough.
Kunai Gun and Perfect Zector from Kamen Rider Kabuto. The first can be used as handgun, knife or axe. The latter is BFS/rifle combination.
The DenGasher and ZeroGasher in Kamen Rider Den-O, which are multi-part weapons whose mode depends on how the parts are combined. The latter is simply a BFS/crossbow, but the former has been changed into a sword, gun, axe, spear/fishing rod, paired boomerang and hand axe, and naginata. Useful things they are.
Kamen Rider Decade's Ride Booker has three functions - a blaster, a sword, and storing the cards he uses to turn into other Riders and use special attacks.
He later receives the Axcalibur when he obtains Infinity Style, which is a sword that can also function as an ax.
Most Super Sentai groups (and, by extension, their Power Rangers counterparts) have laser pistols that become a sword or some other melee weapon for their common sidearm.
Standout examples include Gao Silver's Hustler Rod (a sword, rifle and pool cue), Bouken Silver's Saga Sniper (gun, sword and metal detector) and Gokai Silver's Gokai Spear (trident, spear and anchor). For some reason, they like giving these kind of weapons to Silver Rangers...
Before any of those three, MammothRanger had an axe that turned into a laser cannon (a concept that would be re-used for the U.S. exclusive Titanium Ranger's weapon, and the entire Gingaman team had the Mechanical Blade Kiba (or Transdaggers), which has SIX different modes: fang (its default form, which is used both for one of the team's original finishing moves and for activating and controlling their mecha), short sword, claw, laser crossbow, a pair of daggers and a longbow.
The Qualta Blade in Farscape, which can transform into a pulse rifle.
The phasers and disruptors from Star Trek could be used to stun someone, burn or heat a target, kill, be set on overload and explode, or even disintegrate a target. It was even useful in brewing coffee.
In Andromeda, the Force Lance can fire plasma burst, shoot smart bullets (which are themselves Swiss Army Weapons, because they can target opponents or intercept incoming missiles, bullets, or mortar rounds), shock unauthorized users who touch it, shock the ground near someone, be set on a "lightning" setting in which it can only fire 3 short range shock pulses, expand into a 2-meter long staff (which can shock people it touches, set on overload and used as a grenade, and be used as a grappling hook, cutting torch, or light source.
Tomica Hero Rescue Force has the Rescue Breakers, which are a combination of a rope, an axe, a pickaxe, a hammer, a drill, an analyzer-camera thingy, and a grappling hand, as well as the Rescue Crusher, which has chainsaw, drill (again), and water cannon modes. And then we get into the Max Divider, which is comprised of a circular saw, a sword and another drill.
The spinoff Rescue Fire has the Tri-Basher which has Gun, Sword and extinguisher modes.
The Sonic Screwdriver in Doctor Who, can be used for anything from picking locks to making robots' heads explode.
Just don't bother trying it on anything wood.
Or around hair dryers.
Word of God has stated that the writers have fun trying to come up with new uses for the Sonic Screwdriver.
The Witchblade. Usually it was a bracelet. When the wielder needed it to, it would become a dagger, a short sword, a broadsword, a cestus. It could also become a steel gauntlet, a vambrace, or even a whole suit of plate armor when it had to.
House is a zombie slayer in his dreams, and gets an appropriately cool weapon: his cane can transform into either an axe or a shotgun.
A memorable sketch in the early days of Saturday Night Live featured Dan Aykroyd doing a commercial for the Swiss Army Gun. It featured the usual knife features (utility blade, nail file, fish scaler, corkscrew), along with a .357 revolver, a sub-machine gun, and a mortar (with incindiary grenade). Plus a genuine ivory toothpick. "Isn't that amazing?"
Dungeon Master's Guide: Rod of Lordly Might (mace, sword, battle axe, spear, life-force absorbing device, magic staff, door opener, ladder, target of infinite puns...)
Unearthed Arcana: Rod of Flailing (rod, horseman's mace, footman's mace), Staff-Mace (quarterstaff, great mace, mace), Staff-Spear (staff, spear, long spear), Anything Sword (any type of sword), Hornblade (knife, dagger, scimitar).
Slightly subtler: metalline, a metal that allows a weapon made of it to switch between any kind of special material, such as adamantine, mithral, or silver—useful for overcoming different types of damage reduction.
Magic Item Compendium: The Rod of Surprises, it can be used as a javelin, kama, longspear, quarterstaff, scyth, shortspear, short sword or spear. It can also store messages of up to 25 words to be repeated on command. There is also the Morphing property, that allows a weapon to become any other weapon of the same hand category (i.e. a one-handed weapon with the property can be any one-handed weapon).
Obliterators from Warhammer 40,000 can transform their arms into meltaguns, lascannons and plasma guns amongst others.
A slightly more subtle version is the Shot Selector weapon upgrade in Inquisitor and Dark Heresy- it allows a weapon to hold multiple magazines of different types of ammunition, allowing the user to switch between them quickly.
Combi-bolters are boltguns with an underslung melta, plasma or flamer attached to them. They only have enough ammunition to fire the secondary weapon once. Bolters used by Space Marine Sternguard also count, as they come with various special ammos for different tasks, such as taking out heavily armoured targets or negating cover.
As mentioned above, Humongous Mecha are pretty much already a type of Swiss Army Weapon, but in BattleTech they go one further: the Clans have invented OmniMechs, which rather than relying on fixed hard points that require an entire variant to be redesigned to get a different configuration have modular points that can field virtually any weapon or equipment, as long as there's unused mass and space.
More recently, Bow of Nylea. Pump a creature permanently, shoot down a flying creature, gain a bit of life, or shuffle cards from a graveyard back into their owner's library. Unlike the Jitte, it's not an equip.
One of the items in the original "Munchkin" card game is a Swiss Army polearm. (Depicted as having a number of halberd like blades, apparently able to (against all reason) fold into the shaft.)
In Paranoia, cone rifles and some other guns take multiple types of ammo (armor-piercing, hallucinogenic gas, tactical nuke, etc.) with the same size shells, which are never ever mislabeled.
Boris' crazy polearm from GURPS: Low-Tech is a dueling halberd axe head, pick head, barbed spear point, a second spear point at the butt, a hook and a four yard long kusari (chain) attached somewhere on it. It's hard to even envision such a monstrosity.
Gamma World module GW6 Alpha Factor. The list of New Items includes the Chameleon Rifle. It has interchangeable barrels that allow it to fire as a rifle (single shot or semi-automatic) or submachine gun.
Shadowrun. The AUG-CSL Weapon System in the 1E/2E Street Samurai Catalog can be assembled as a submachine gun, carbine, assault rifle or light machine gun.
And 4E has the HK XM30 (based on the XM-29 and the XM8) mentioned under Real Life. Baseline, the XM30 is an assault rifle with an underbarrel grenade launcher. Using different kits, you can modify it to have an underbarrel shotgun, become a carbine rifle, sniper rifle or a light machine gun.
The weapon obsessed Hellvetics from Degenesis have the Trailblazer, a tri-barreled rotating automatic rifle who's stock can be turned into a bipod, a grenade launcher, a bayonet, or a pair of useful pliers. Amusingly, the Hellvetics (as can be discerned from the name) have literally evolved from the Swiss army after the apocalypse.
Exalted has a few of these, but the most prominent example can be found in Wonders of the First Age; the Power Mace. An ornate-looking club, originally devised by the Mountain Folk, once activated it projects an Essence field with two settings; burning lethality, or blunt impact. The shaft also contains a built-in miniature Essence cannon, which can also fire in both lethal and non-lethal modes.
Classic Traveller, Paranoia Press's supplement SORAG. The Smallarms System is a package of interchangeable parts that can be used put together to create a submachine gun, an assault rifle, a carbine or a light machine gun. It has several accessories as well, including a folding stock, a shoulder stock, electronic sights and a silencer. It is stored in a fitted attache case.
The Morrow Project. The Stoner weapon system is a kit consisting of one receiver and several different types of barrels, feed mechanisms and stocks. They can be assembled into any one of a number of Stoner weapons: Stoner M23, Stoner M207, Stoner Mk 23 and Stoner M22.
As its name suggests, Jude's Shapeshifter from Wild ARMs 4 can take many forms. Throughout the game, Jude has used it as a pistol, a sword, a shield, a sub-machine gun, and a shoulder-mounted beam cannon.
Wild ARMs 5 loves this trope even more. Dean has a pair of pistols with long magazines that can be used like tonfas; Greg's BFG has a Laser Blade in the detachable rear grip; Avril's sword can become an energy whip; and Carol's backpack shoots at least three different kinds of missiles.
The titular weapons from the Soul Edge and Soul Calibur games are legendary swords which can change form to weapons more suited to their wielders' fighting styles. Some of the characters from the games also wield transforming weapons themselves, such as Ivy Valentine and her sword/whip, or her father Cervantes de Leon and his sword/pistol (paired with a normal sword). There's also Necrid from SCII, who wields a glowing ball of energy which can transform into a number of different weapons suitable for the moves he copies from other characters.
Ignoring the Canon Discontinuity for a moment, Krystal's staff (which Fox steals) from Star Fox Adventures is the main way in which Fox interacts with his environment. He can use it as a blunt killing stick, a basic blaster, an ice blaster, a mini-earthquake maker, an impromptu switch, a basic lever, a mini-rocket, a Mook disguise, and a magic door key.
One could probably count Samus' Arm Cannon from Metroid as well, since it can open up into a missile launcher.
And, in the first two Prime games, it can switch between four different beams, complete with a slightly different physical configuration for each one.
Zero Suit Samus in Super Smash Bros. Brawl's stun pistol transforms into a laser whip.
In Metroid Prime, she has a power beam, a wave beam, an ice beam, and a plasma beam. She can fire a charged beam and a charged combo (which uses missiles) from any of those. She also has the missiles. Finally, she also gets a phazon-based weapon in the boss fight. That gives her fourteen weapons she can fire from her arm cannon. There's also her grapple beam, which isn't a weapon, and two different kinds of mines that can only be used when in the morph ball. If you're willing to count those, that makes it seventeen.
A nice little touch: The HUD identifies the four beams with Chozo hand signs. If you use the X-ray visor, you can see Samus's hand making those signs inside the gun.
Hard to tell if it's the same in Echoes, since the weapons are identified by simple symbols. And in Corruption, using the X-Ray/Thermal Visor shows that the PED-enhanced Arm Cannon just has a type of trigger inside of it.
Even the Grapple Beam becomes a weapon in Corruption. Now Samus can yank away an enemy's armor or shield, and with later upgrades even use it to siphon energy to or from a target. This can be used to absorb health from or electrocute enemies.
Mag, the main character in the Evolution game series had a literal Swiss army weapon. It was a giant Swiss army knife strapped to his back that could toss bombs, shoot flames, wield hammers, and heal amongst other things.
The "Assault Rifle◊" used by the associated powerset in City of Heroes/City of Villains has an improbable number of alternate fire modes and non-removable integrated weapons, including the titular assault rifle, a shotgun hot-swappable between regular shot, slugs and beanbags without reloading, a grenade launcher, a sniper rifle, and a flamethrower. And that's without the rocket launcher and freeze ray addons. Weapon customization was later added to the game, allowing Assault Rifle users to choose more conventional-looking skins for their weapons if they want them. It's still a frankengun, but now it no longer has to look like one.
The Mechswords from Atelier Iris 3 can change shape to do a variety of things, including extending a superheated alchemical prod or firing shuriken.
The player character from Maken X is a sword with the ability to possess those it defeats in combat. It can then change itself into a form that suits them.
All of the weapons in Painkiller have two drastically different firing modes. In order of acquisition, a buzzsaw with a launchable auto-retracting warhead, a shotgun that can fire liquid nitrogen cylinders, a grenade launcher that also shoots stakes, a lightning-firing shuriken launcher and a chaingun-plus-rocket launcher. The expansion Battle Out Of Hell adds a flamethrower-plus-SMG and a rebar launcher with a multi-explosive attachment. The third part, Overdose, adds even more combined arms fun.
All of the weapons in Project Snowblind also have drastically different firing modes. Especially interesting is the silenced stealth pistol that can fire missiles, the shotgun that shoots sticky bombs, and the sniper rifle that can fire mind control bullets.
The Sparda weapon from Devil May Cry shifts between a BFS, a pike and a scythe when you do particular attacks. The Kalina Ann rocket launcher from the third game has a grappling hook bayonet and a cluster micro missile launcher attached. (After all, isn't the only thing better than rockets, more rockets?) Nevan from the same game normally acts as a guitar that shoots electricity and bats, but some of its abilities cause it to transform into an electrically-charged scythe. And the fourth game gives you Pandora's Box, which has at least six forms, including a crossbow, a rocket launcher, a giant frikkin' laser cannon, a chaingun, a fan-blade boomerang and a flying Macross Missile Massacre platform.
Also, the in-game description of Pandora's Box mentions the weapon having 666 different forms.
The aptly-named Multiple Weapon Systems wielded by Shion and Miyuki in Xenosaga. It's a giant square shield/gauntlet thing attached to the back of the arm which contains electric rods, a fire bomb launcher, a giant blade, an antigravity device which enables an ordinary scientist to carry it, and more. But only in the first game. Shion later gets a more streamlined and compact version in the second and third games, while Miyuki brings back the big orange brick for her Guest Star Party Member stint in the third game.
KOS-MOS could be defined as one. She does.
Speaking of gun/sword combos, the gunblades from the Final Fantasy series. The original from Final Fantasy VIII is an odd non-example, since the "gun" mechanism only sends a shockwave through the blade at the moment of impact and can't actually be used to fire projectiles; however, later Final Fantasy spinoff media includes variants which fully function as both guns and swords, such as Loz and Yazoo's bladed rifles in Final Fantasy VII: Advent Children, and Weiss's katana rifles from Dirge of Cerberus: Final Fantasy VII. Lightning, the heroine of Final Fantasy XIII, also wields a weapon which can switch between the forms of a sword and machine gun.
Other Final Fantasy XIII weapons do this as well as the characters gain longer ATB gauges. While Lightning's weapon switches between sword and gun as mentioned above, Fang's changes from a spear to a Sansetsukon triple staff with spikes on the end to stab. Sazh's dual pistols transform into an assault rifle or shot gun at the end of his combo. The sequel continues this trend with Serah's bowblade, which switches between sword and bow forms, and Noel's dual swords which combine into a spear.
Barret's gun-arm in Final Fantasy VII perhaps. He starts with a Gatling Gun and gets some other machine guns, but also gets a mace, shears, a chainsaw, laser guns, a drill, rocket launchers, and even an oversized fist. Since the gun was grafted onto his arm, that "base" must be constant while the business end is changed.
Of course, it's big enough that even he can't wield it as you would a proper sword; in that form, he has to drag it on the ground (complete with sparks and damage to the floor), and swing it around himself in order to attack with it.
Above gunblades aside, Shin Megami Tensei: Soul Hackers gave us the GUMP, or Gun COMPuter. The computer lets you summon and control demons to do your bidding, and the gun lets you shoot things, as opposed to the other way around.
Cupil in Skies of Arcadia is a Swiss Army Weapon of sorts. If given enough "chams", he gains the ability to transform into a new, stronger type of weapon, which falls into one of two broad categories: a cutting weapon, such as a knife or sword, or a bludgeoning weapon, which makes a mildly humorous "donk" noise when he connects.
The upcoming cancelled FPS Tiberium from EA, set in the Command & Conquer series, hands such a device to the lead character instead of the typical mass of weapons available in a FPS.
Jak's Morph gun that he gets in Jak II starts out as basically a shotgun, but gets mods to become a rifle, machinegun, and BFG. In Jak 3, it also gets mods for a ground wave, reflecting laser, electric arc, anti-gravity wave, grenade launcher, Attack Drone, homing needlegun, and finally a pocket nuke. In TLF, the Gunstaff goes back to the original four.
A mild example can be found in the Silencer's armor of Crusader, which can use a series of different batteries, mount multiple different types of shielding, allows an infrared-viewing chip to be placed in the visor, has a surprisingly large backpack that's apparently bolted on, a datalink (PDA with wi-fi access, effectively) mounted in one arm, a holster designed for multiple pistol types on one hip, and can even power energy weapons. And, of course, it's hella stylish.
Mega Man's buster arm in the classic and Mega Man X series can reproduce any projectile gained from defeated bosses. This includes but is not limited to: Fire, ice, lightning, bubbles, leaves, whirlwinds, swords, missiles, bombs, boomerangs, soccer balls...
If Cerveau is to be believed, the Triple Rod, Chain Rod, Recoil Rod, and Shield Boomerang are all functions of the Z-Saber in Mega Man Zero. In the sequel series, the titular Rockman Model ZX has a single weapon that is a pistol or a sword.
In World of Warcraft Benediction, a healing staff, could - at the owner's whim - be morphed into Anathema, a damage dealing weapon (this transformation worked both ways). Likewise, hunters had access to a bow that could morph into a staff and back.
From the same instance also comes Thunderstrike/Shadowstrike, a polearm that could transform between two forms, each with a different chanse-on-hit-effect. Other than the procs, neighter form had any other stats, making it the weapon universally known as Vendorstrike.
Furthermore, some weapons or other equipment double their normal purpose with other things. Like opening portals to a certain location or producing drinks out of nowhere.
Unreal II: The Awakening sports a grenade launcher capable of firing six different types of grenades (high-explosive, incendiary, toxic, EMP, concussion and smoke).
The Unreal Tournament series weapons fall under this as well. Notable examples include the Flak Cannon (a shotgun/grenade launcher), the Shock Rifle (a gun which shoots laser beams and laser balls, the latter of which can be shot by the former to create a powerful explosion), and the Link Gun (which can rapid-fire green pellets of death or a constant stream of plasma; both hurt enemies, but from 2003 onward the latter powers up allies with a Link Gun equipped and repairs friendly vehicles and control nodes).
UT 99's rocket launcher has features which combine into seven different firing modes: launch of single rocket, launch of multiple rockets in a spread, launch of multiple rockets in a solid cluster, launch of homing rockets, launch of single rocket as grenade, launch of multiple rockets as grenades in a spread, and the same in a cluster. (If only it made coffee, life would be complete.)
Discounting the fact that Humongous Mecha are giant walking Swiss Army Weapons by default, the Weissritter (Excellen Browning's personal unit) from various Super Robot Wars games is armed with the Oxtongue Launcher, which can fire a laser blast or large artillery shells (or both at once in its Limit Break). Somehow, it seems to switch modes depending on how many times it is spun around the mech's hand before firing.
This is because it is two guns fused together along the barrel, so you have to flip it to use the other gun. The Oxtongue Rifle is far more streamlined, and incorporated into one gun whose mode shifts are controlled by software
The spinoff RPG Endless Frontier features Haken Browning (who despite the name is more like the expy of Excellen's boyfriend) and his Night Fowl, an assault rifle with an underslung stake driver and a fold-out blade in the stock, which he wields with a similar amount of gun-twirling flare.
Sanger Zonvolt can do pretty much anything with the BFS on his best unit, because he's just that awesome. It's still just a sword, though, and not an actual Swiss Army Weapon. Until he morphs it into a machete/boomerang, anyway.
The Landgrief has the "Incision Knife", a gigantic combat knife that can transform from a traditional pigsticker into what looks for all the world like a pair of gardening shears. Maybe its for clearing a path during jungle fights. Or maybe they just like really big topiaries in the Shadow Miror Universe.
The Gunleon from Super Robot Wars Z has a giant wrench... until suddenly it is turned into a three-sectioned staff and used to really kick some ass in the vein of Bruce Lee (but not enough to clone him).
Also from Super Robot Wars Z, the Virgola is armed with a coffin like thing. Each of your three Virgola start with a different attack using it, and by the end, Setsuko gets to use all three with the one... coffin... thing.
And from Z2, Brasta's EAGLE, which is a machine gun, grenade launcher, net gun and sniper rifle in addition to having a beam bayonet function. Brasta's shield doubles as a jet-propelled/melee weapon as well.
Redline featured a rifle whose barrel could transform into a variety of weapons, including a shotgun, assault rifle, grenade launcher, and even a rotary saw. The rotary saw could also act as a propeller, launching the player across the map if they jumped while using it.
Star Wars: Republic Commando gave the player the DC-17m blasters which could be configured from its standard automatic blaster form into a sniper rifle or a grenade launcher, complete with characters changing parts on-screen.
The novels to the game have Verpine weapons which don’t technically change appearance or function but can be loaded with ANYTHING including rocks and candy.
Mass Effect has the aptly named omni-tool, which is essentially a futuristic wrist mounted cell phone. One of its many feature is a mini-fabricator, which is essentially a 3-D printer which the player can use to recycle old junk and create new stuff from that junk like mods or repair kits. Or weapons. In fact, with the right mods, the omni-tool can do almost anything. Additional mods give it an even greater range of abilities. A list of just some is included below.
Creating a huge blast of energy around the user, knocking any nearby enemies to the ground.
Firing off electric blasts that disable shields and weapons, stun enemies, and kill robotic enemies.
Doing the same thing as the above, except instead of simply disabling the enemy shields, it can drain the enemy shields to boost the users' own.
Flash fabricating diamond-hard swords, power fists, cattle prods, batons, and flaming buzz saws.
Inflicting severe head trauma with it, by supposedly driving a spike of the generic compressed matter (omni-gel) into your opponent's head, and remotely causing extreme pain in your opponents nervous system as well as disabling their bodies.
Acting as Freeze Ray that fires a mass of super-cooled subatomic particles capable of snap-freezing targets instantly, causing them to fall on the ground and shatter.
Firing large blades that stick to their target and explode after a few seconds.
Causing enemy weapons to backfire and hurt them.
Deploying small friendly drones that shoot rockets at the enemy and explode upon death.
Projecting a full suit of Hard Light armor. (Okay so its not actually hard light armor but it acts in a similar fashion).
The keyblade from Kingdom Hearts is a legendary magical weapon, but is gotten very early in the game. Instead of getting new weapons, your weapon upgrades take the form of keychains which transform the keyblade into new and more powerful forms.
The Bonus Boss of Kingdom Hearts II Final Mix+ takes it over the top: Over the span of the Battle, he can turn his keyblade into a whip, a giant energy cannon, a longbow which fires arrows which screw up your menu, some sort of clockwork-punching-glove and even a hoverbike.
The Johnny 5 (probably a play on the Johnny 7, see Real Life section of this page) in ZPC: machinegun, shotgun, laser zapper, grenade launcher and super-disintegrator. Whether it's been done this way for massive sprite recycling power is left to the readers.
Technically, the weapon from Eradicator is one of this, but none of the forms look remotely similar to one another nor is there any animated transition between them, so it's probably just the manual trying to justify one guy/girl/alien carrying a huge arsenal by him/herself.
Most of the guns in Perfect Dark have multiple functions. The Dragon's main function is a powerful assault rifle, but flip a switch and it becomes a land mine. Anybody who touches it is blown to smithereens. As one can imagine, the gun is a BITCH in multiplayer.
Unless you have the other gun which is a light carbine with a built-in mine detector.
Not to mention the Super Dragon. It had the firepower of the Dragon, but instead of becoming a proximity mine, it could become a grenade launcher.
The Laptop Gun takes the cake, its default form is a functional laptop (well, the screen at least lights up) so you can sneak it into a secure area. Once you're ready to do your dirty work, it does some flipping and folding and turns into a machinegun. And if you need to cover your escape, throw it at a wall and it will do some more flipping and folding and turn into an autonomous sentry gun.
darkSector features a bladed disc weapon called the Glaive. As well as being able to throw it, by the end of the game you can power throw it for quadruple damage, guide it in flight, use it as a flashlight, use it to pick up distant objects and return them to you, absorb elements and use them to damage your enemies, absorb elements and use them to cause explosions, generate a force field that reflects all enemy fire to your weapon's crosshair, and turn yourself invisible with it. Oh, and you can also hit people in the face with it.
Tron 2.0 has a basic set of weapons (a disc, a stick, a virus ball and a "machine gun") which can transform to many other weapons, for example, the stick can transform from a close combat stun rod to a sniper rifle.
Septerra Core does this to some people of the party through upgrading the weapons with add-ons. As an example, the machine gun of the main character gets the ability to shoot grenades (normal ones, napalm grenades and cluster grenades), energy beams and seeking missiles.
Pretty much why the aforementioned M4 Carbine is the signature weapon of both Metal Gear Solid 4: Guns of the Patriots and Americas Army: Special Forces, as their most customizable weapon. Perhaps in indirect imitation of this, assault rifles seem to have become the most "do it all" modular weapon type in first-person shooters that allow attachments and some degree of precision aiming (such as aiming through the sights).
The player's main (and only) weapon system in Codename: Outbreak is a giant rifle-like weapon with a rotating barrel, where each "slot" is a different gun with its own ammo, including a sniper rifle, a silent (not to the player) laser, an assault rifle, and a laser-guided rocket launcher. The weapon also includes an infrared scope and a parabolic microphone. The player is also incapable of picking up enemy weapons, only their ammo and other supplies.
Ricardo of Shadow Hearts: From The New World carries an acoustic guitar. His normal attack turns the neck into a machine gun and the body into a shotgun. Some of his Serenata attacks, in turn, turn it into a flamethrower and, in his most powerful, a multi-barrel missile launcher. And it still plays sweet music!
Wizardry 8 has the Omnigun given to the Gadgeteer class. It starts being able to fire bullets and rocks. As it is upgraded, it gains more and more versatility.
Cryptosporidium's gun in any of the Destroy All Humans! games starts off just being able to shoot electricity, but each datacore you pick up adds another mode of fire, from heat rays and grenades to anti-gravity buzzsaws and remote control anal probes.
Although not used for said purposes during the story, the Seventh Scripture in Tsukihime has numerous abilities. The basic redesigned form made it from an antireincarnation weapon into something that can also fire holy harpoons like bullets. That's instory still, though. Some mentioned other uses note that the weight can be doubled if you add all the various optional pieces to it. Also comes with the spirit of a teenage girl with hooves and strange ears. Order now and we'll include the customized industrial model with four random dots on it!
In The Conduit, the ASE (All-Seeing Eye) can find hidden caches, hack computers, show the path to the next objective, detonate mines, and reveal invisible switches and enemies.
Iji's gun can function as any of quite a lot of different weapons, once she finds an example of said weapon to copy and has a high enough level in the appropriate skill.
In Tales of Vesperia, the character Yeager has what appears to be a Scythe, a crossbow and a rifle all in one.
Hubert Ozwell of Tales of Graces uses a pair of small swords that also function as pistols. He can join them together to form a double-bladed weapon, which can in turn act as a bow for him to fire energy arrows from.
The Sacred Clay weapons in RuneScape can transform between the three different combat styles, and the tools can transform between many useful tools like needles, fletching knives, hatchets, and butterfly nets.
Memebers now also have access to the Dwarven Army Axe, which combines the functions of a hatchet, pickaxe, needle, tinderbox and chisel into one item. While nowhere near as good as a specialty pick or hatchet, being able to cram five tool into one inventory slot is very useful when traversing dangerous areas of the world that need those sort of tools to get around.
Monster Hunter Tri introduced the series to the Switch Axe. A mechanical weapon that folds out into an axe when you take it out, and can be rearranged into the shape of a huge sword that explodes on each swing.
The fourth installment in the series introduces the Charge Axe, a weapon that starts off as a sword and shield, but can be joined together into a massive blade that makes even the greatswords look rather modest by comparison.
Namco Bandai's thoroughly anime response to Monster Hunter, Gods Eater Burst, hands your player character a weapon that can transform into an enormous sword or a gigantic cannon. You can also customize the parts.
While not a transforming weapon, Executioner Majini of Resident Evil 5 fame, both in game and in the latest movie, lugs around a very big weapon which is something like an axehammer, both axe and hammer molded into one to form the weapon's huge head.
In Jet Set Radio and its sequel, the player character can use 'spray paint' to kill police officers, give their rollerblades a crazy boost, disable machinery, cover spotlights, disable bomb timers, operate switches.....
The protagonist and antagonist in Nanobreaker both wielded plasma swords which could seamlessly alter the shape of the blades from a simple katana shape, into a greatsword, into an axe, into a scythe, and an enormous hammer. And that's just over the course of one combo.
Lifeforce: Tenka has a multimode weapon that changes appearance as plugins are collected.
Beyond the Grave from Gungrave carries a large steel coffin on his back that acts as his gun rack, impromptu JATO device, machine gun AND rocket launcher. Also works really well if you smash a mook in the face with it. Also has a spike that lets Grave plant it in the ground so the jets can spin it around and fire a machine gun in a 360 degree arc of death.
Star Wars: The Old Republic: The Republic Trooper's weapon becomes this no matter which Advanced Class is chosen. Besides standard beams, it's a grenade launcher, mortar launcher, AOE ion pulse, a Healing Shiv, and more.
The Dream Dagger in Neverwinter Nights 2: Mask of the Betrayer can be shapeshifted into any weapon your character has the weapon proficiency feat for.
Team Fortress 2: The Pyro's flamethrower is surprisingly versatile for a flamethrower. It can set enemies on fire (obviously), reveal disguised or cloaked Spies (by spraying flame onto suspicious-looking players or empty spaces), give a friendly Sniper literal firepower by setting his Arrows on Fire, blow away enemy sticky grenades with the airblast, blow away enemies in general, extinguish burning teammates, reflect rockets, grenades, arrows, baseballs, and pretty much any other projectile that isn't a bullet, shotgun shell, or syringe.
While already kind of qualifying as a "weapon" herself, Peacock in Skullgirls is equipped with a device called the Avery Unit which gives her access to a seemingly infinite array of weapons and explosives (most of them based around the "Silver Age" of cartoons, and at least some of them sentient).
Dungeons of Dredmor has the quite literal Dwarven Army Sword, a sword, axe and mace all in one.
The player's primary weapon in Extermination is the SPR-4, which seems to take its cues from the real-life M4A1 SOPMOD. The rifle is endlessly customizable, with everything available from the run-of-the-mill optical sights, underbarrel shotguns/grenade launchers and trigger mechanisms to a flamethrower and even a guided missile launcher.
God of War has the chained blades of Kratos (Blades of Chaos/Athena/Exile). First of all, the chained blades are both melee and long range weapons: you can stab minotaurs in the mouth with them or smash and slash advancing hordes of undead before they reach you. You can also use them to move around: swing like Tarzan or climb walls (or ceilings) with them. Or pull enemies to you or you to bigger enemies. Or pin elder gods to ground. Or crop gigantic horses. The possibilities are endless! Oh, and they are on fire.
Xenoblade has the Gunlance, wielded by Reyn and some other soldiers. It's an enormous spear/sword combo- that extends into a shield with a hammer, and has a rifle attached to it. And it's held with one hand.
Unfortunately you rarely see most of this cool functionality, as Reyn mainly just whacks things with it. For extra Bad Ass points, he uses his other hand to punch things.
Unusually for this trope, the opening cinematic actually shows why such an overdesigned weapon is standard issue for some military units. The Mechon it's designed to be deployed against have deadly projectile weapons, hence the shield part, and are Nigh Invulnerable to normal weapons themselves, requiring a heavy mass and sharp blade to punch through the armor, then a small cannon shot to inflict any meaningful damage. Unwieldy and only partially effective, yes, but there's only one Monado and that does horrible things to people if they wield it for too long.
In Pandora's Tower, Aeron does an impressive job of turning the Oraclos Chain into one of these. He can rapidly lash enemies, strip their weapons, tie up a part of their body and drag them around, spin an enemy around like a flail and then fling them away, chain two enemies together so damage to one is copied to another, rip items out of fallen foes, monitor Elena's curse, grab stuff out of normal reach, anchor to certain objects to swing across gaps, activate levers and other devices, anchor large enemies and bosses to the environment so he can reach their weak point, rip out a boss's heavily defended heart, and detect which room in their modest safehouse his girlfriend happens to be in at the moment.
Jayce from League of Legends has his Mercury Hammer, which he can convert into a Mercury Cannon to switch from being a melee champ to a ranged champ as the situation demands.
The Gunslash weapons from Phantasy Star Online 2 essentially combine the handgun and one-handed sword from the earlier games into a single weapon, and can be changed between their gun mode and sword mode with the touch of a button. A number of its photon artes utilize both modes, generally beginning with slashes then finishing with a gunshot.
In Banana-nana-Ninja! Baninja uses an Omni-Functional Kitchen Gadget to win the Feast Master cooking tournament. The OFKG "transforms into any cooking tool you could possibly need, and dozens more that you couldn't possibly need, ever!" It is used as a saucepan, a range, and later a Humongous Mecha.
It's easier to list the weapons in RWBY that don't fall under this.
In Clockworks, Thorton's bow has blades attached to the limbs, thus making it an effective melee weapon as well.
In Goblins, Dies Horribly had his hand replaced with a shape-shifting living metal thing, which can imitate a normal hand, becomes a ridiculously spikey gauntlet when he's frightened, and has been used as a grappling hook and a long-range stabbing implement.
There are several examples in MS Paint Adventures. In Problem Sleuth, there was a running gag that weapons could turn into innocuous items, such as a tube of lipstick into a chainsaw and a paintbrush into a whip. In Homestuck, Kanaya wields a lipstick/chainsaw as a Mythology Gag, while Jane has a spoon that can turn into a fork at the flip of a switch.
The BFGs used by the cast of AH.com: The Series were eventually established to be this, in order to cover inconsistencies in how different authors had portrayed them in the past.
Draven Rowe's magipunk crossbow can rotate the stock to reveal any of a number of useful wands.
The Abstract Weapon from Ra. It can turn into pretty much anything that could be useful or helpful in destroying stuff. It also constantly gives it user new suggestions as to who to kill next to advance their goals.
Every second you spend holding it, it's throwing possibilities at you, telling you how best it can be used. It contains every weapon ever made. It contains every weapon never made. It is the primordial destructive spell. It is the prototype for all human violence. There is a List inside it, which... I cannot describe the List.
In Rock-A-Doodle One character use an actual Swiss Army Knife as a weapon. His Rummage Fail can reveal such items as flags, flowers and umbrellas. The last item he uses is a flyswatter.
In Avatar The Last Airbender, Aang's staff doubles as both a melee weapon and a personal flight device. In the third season, he gets a new staff that has the same functions, but has a small snack compartment built into it.
Trevor Goodchild, nemesis of Æon Flux, carries a multifunction cigarette case and lighter that transforms into a derringer. In one episode (A Last Time for Everything) it's highlighted as a MacGuffin.
Aeon's own weapon of choice, the FUG (Flux Universal Gun) is also fairly modular. It can be loaded with numerous different types of ammo, including rapid fire flechettes, high explosive shells, high explosive robot spiders & of course, pressurized gas cartridges & a grapple.
Ulysses 31. Whether you regard it as a laser gun with a lightsabre or a lightsabre with a laser gun either way there is not much else you need.
Galtar and the Golden Lance: the titular hero wields the titular weapon as a pair of sabers, which can join together at the pommel into a Double Weapon or combine into a more powerful sword, it also retracts into a double pommel shaped stick.
Stan: Pen-gun — Mightier than the sword! Sword-gun — mightier than the pen-gun!
One episode of The Tick had a squad of Swiss Mercenaries who carried what looked like giant swiss army knives-which folded out into an array of weaponry, including a flamethrower.
The multi-purpose Swiss Army Knife, of course. It's the Trope namer after all. The standard Swiss Army Knife doesn't have that many functions (not even a corkscrew) compared to other models, some of which can be used as a memory stick or MP3-player in addition to a varying degree of functions. The most expensive one has 85 devices and 110 functions◊.
Both of these, of course, are mostly not supposed to be weapons. And given the relatively short (and in most models, non-locking) blades, they'd make rather poor weapons. Even more standard knives for other militaries are generally not designed for the sole purpose of killing someone - it's an add-on.
That 85-tool knife is Awesome but Impractical, since it's clearly too unwieldy to make effective use of most of the functions. (Does "bludgeon" count as a function?) In fact, that's the point. It exists to show off all the tools that had, at the time, been implemented in a Swiss Army Knife. Relatively more practical (though still quite large for pocket use; a belt holster is a must) is the "Swiss Champ" model (the largest standard-production Swiss Army Knife), with 22 tools and 33 functions.
One episode of Law & Order: Criminal Intent had Detective Goren gleefully mess about with one to force an antique store owner to say where he got a certain piece of merchandise (which he was avoiding showing its rightful owner in the cold opening).
The XM-29 SABR◊, more commonly known as the OICW, was designed to complement the M16 family; originally, it was supposed to replace the M16 entirely. It features a laser telemeter, a fire control computer, an IR/NV camera scope with adjustable zoom, a 5.56 mm carbine, a magazine-fed 20mm grenade launcher [later 25mm] with user-set fusing, and an optional bayonet. Which must have been like trying to stab someone to death with a television set.
The Daewoo K11◊ uses the same layout and general concept as the OICW, with the added bonus that it's actually seen limited service (and even limited test use in actual combat in Afghanistan).
The AICW, basically the same thing without the second magazine.
Many modern weapons are becoming more modular in this way. A good example is the XM8 modular carbine, which in addition to the basic weapon could be easily switched between grenadier (just a swap of the front end), (even more compact) carbine, "automatic rifle" (light machine gun) and designated marksmanship rifle (not quite configurations; eventually the latter two (sharing the same barrel length — that of an M16) would simply be combined into one full auto-capable rifle with a light machine gun magazine and a 4x scope.
The AR-15 family of weapons has had this modularity for decades - the entire upper half of the rifle (barrel, bolt group, and sights) can be swapped by pushing out two pins. The SOPMOD package for the M4A1 carbine included, at one point, a short barreled upper half (CQBR) and a light sniper rifle upper half (SPR). Both were eventually issued as standalone weapons, but the concept is essentially the same as the H&K XM8, perhaps shedding light on why the latter wasn't adopted at the end of the day.
Going back a ways, the medieval halberd combined the functions of a pole-axe and a spear, and it also had a hook useful for pulling enemy cavalry off of their mounts (and it also doubled as a counterweight to the axe-blade, improving the halberd's balance). Some halberds also had a weighted base which could be used like a mace if it wasn't sharpened into a spike and a reinforced shaft to block weapons.
The halberd, of course, having been used prominently by the early Swiss armies, is a literal Swiss Army weapon.
The amusingly-named Bohemian earspoon combined a pick with a spear for flexibility against armoured foes.
The Bec de Corbin and Lucerne hammer both combined the warhammer with the pick and spear.
The pollaxe is a combination short spear, axe or war hammer, and spike or hook.
In fact most of the later polearms combined at least two functions be it axe, spear, hook, hammer or spike; the shorter ones could also be used like a staff.
The Hall flintlock rifle had a breech-loading action which could be removed entirely and used as a somewhat ungainly pistol.
There was a period in black powder weapon history where various melee weapons - including maces and swords - with a gun in them became fashionable. Their actual utility is questionable. Tools could also contain (sometimes poorly concealed) weaponry; there is a set of cutlery with miniature flintlock pistols at the end. The book suggests you shoot the cook if your steak is too stringy.
Likewise, in the Old West, ammo was of poor quality and couldn't hold up to the rigors of the environment, so it was common for pistols to have a short blade or a thick barrel to be used as an axe or club in close quarters. Some revolvers also had "skull crusher◊" grip design; if ammo ran out or failed, you could hold it by the barrel and crack some heads.
Modern bayonets, which can often be used as wire cutters in conjunction with the appropriate sheath. This came into common use with the bayonet for the AK-47.
The Chinese military allegedly had a version of their standard-issue bayonet that could function as a three-shot deringer.
Really, bayonets in general. Originally, because muskets took so long to reload, musketeers were escorted by pikemen to keep cavalry charges from dispersing their formations. Then someone got the idea that you could just attach a blade to the end of the barrel and give everyone a musket.
Many modern military knives feature a mini compass in the pommel, which unscrews to reveal a mini survival kit.
An aircraft example: The Joint Strike Fighter. Designed to be modified as needed for Air Force, Navy, or Marine forces, it can do Air Superiority (like an F-15), Tactical Bombing (like a B-2), or Close Air Support (like an A-10).
Its major transforming gadget is an entire VTOL (Vertical Take-Off and Landing) system. That's pretty awesome.
On paper, it's awesome. In reality, trying to cram so many functions and satisfy so many service requirements created an aircraft that is a very expensive jack-of-all trades master of none. It can do air supremacy, but not like the F-15 and certainly not like the F-22. Its maneuverability is lower than that of the F-16 (and that's for the Air Force version, the Navy and Marine versions are even worse), its stealth worse then that of the F-22, and its radar inferior to an upgraded F-15's. Bottom line, in long-range engagements, it would lose to an F-15 and in a short-range engagments to an F-16, don't even consider sending it against F-22's or Russian PAK-FA. The Navy won't use it for air supremacy; that's why they bought the F/A-18 E/F/G and its AESA radar. For the tactical bombardment part, the aircraft is crippled again by its low stealth compared to the B-2 and the fact that it carries about as much as an F-16 despite an empty weight twice as large. As for the Close Support part, it's way inferior to the A-10, again, because of the low carried weight and also because of the high stall speed, less armoring, and shorter loiter time compared to the A-10. Probably why the USAF decide to keep the A-10 in service well into the 2040s, which is the time when F-35 will start being taken out of service,.
The aircraft carrier version, the F-35C, has the embarrassing distinction of having been designed in such a way as to make it incapable of actually landing on a carrier; the main landing gear is so far aft that the arrestor cable doesn't have time to rebound from being trampled by the wheels before the arrestor hook passes over it.
The Shaolin Monk's Shang Guo or Twin Hook Sword. Serve as swords, hooks, daggers, can be used to parry, and you can hook two blades together and swing them as one double-length weapon.
The simple yet oh so effective trench knife. Knuckleduster guard, a several inch-long knife blade, and a hardened pommel nut for breaking open someone's skull.
Similarly, the pata: a cross between a sword and a punch knife with a buckler built in. Presumably good for bashing as well, though I can't see a situation where you'd want to bother.
The entrenching tool. It's basically a small shovel that can be folded away for easy storage, but it's a critical tool of war that goes all the way back to Julius Caesar's time. Not only can it be used to dig trenches and pits, it can be used as a short-ranged weapon- some models even have concealed blades or serrated edges for cutting ropes and sawing wood. Others simply have sharpened edges on the shovel...or troops sharpen them on their own. During World War I, German trench raiders often carried only an e-tool and a pistol.
The Le Mat revolver of the mid-19th century fired pistol bullets, and also had a single-shot barrel under the main one, containing either a charge of buckshot or a heavier-calibre pistol bullet than those in the cylinder.
While the Kukri cannot shape-change, it has a multitude of uses aside from people-carving (a function it performs reasonably well at). It can be used as a machete, a meat cleaver, and can sometimes even cut wood. Traditionally, the scabbard also holds a pair of smaller blades, the karda for general utility and the unsharpened chakmak for sharpening the kukri and for starting fires with a flint.
The machete itself performs a lot of these functions itself, in addition to its intended role in harvesting sugar cane or clearing brush.
While technically not a dedicated weapon (no matter what certain anime tell you) the kunai of ancient Japan certainly had the capability for being used as one, either as a truncheon or a stabbing weapon. Japanese peasant farmers realized this.
The shotgun is itself a pretty versatile weapon, capable of loading anything from light birdshot to full slugs, or a variety of more specialist rounds like tasers, grenades, Dragon's Breath, flares, etc.
37mm and 40mm grenade launchers can perform most of the above, but on a bigger scale.
Speaking of shotguns, the PancorJackhammer, besides also potentially being fully automatic, had a drum magazine that can be used as an anti-personnel mine.
The lantern shield. That particular example is a shield, blade, gauntlet and spikes all mashed together in one item. You can also hang a lantern from it.
The AK-12, a new Russian assault rifle, comes fresh from the factory firing the 5.45x39mm round that is standard for the Russian military; however, it can be converted to fire the 5.56x45mm, 7.62x39mm, 7.62x51mm, 9x39mm and the 6.5x38mm cartridges as well. The Russian government says they are also working on a brand new 6.5mm round exclusive to the weapon. Oh and one can convert the weapon from an assault rifle to a light support weapon, to a designated marksman rifle, to a carbine and then to a compact carbine. It can also be converted into a 12 gauge shotgun. This is on top of a variety of accessories including a grenade launcher and a variety of optics. Long story short: It can be chambered for more cartridges than one could possibly need, can mount all the accessories that come standard with the AK-series of weapons and can do the job of an array of different weapons. Oh yeah and the shotgun part. Seriously, what more do you need?