Amanda Ripley of Alien: Isolation at one point manages to repair a motion tracker unit using parts from a children's toy. She also crafts her own medkits, explosives, and electronic decoys from random gubbins and scrap metal parts she finds lying around the station.
Arcanum: Of Steamworks & Magick Obscura allows players to be Gadgeteer Geniuses, eventually building such things as steam-powered robots, staffs that shoot lightning, and a device that can revive the dead.
Jan Jansen from Baldur's Gate II starts the game with a crossbow (including bolts), gloves, boots, and goggles of his own design, most of which give him a big bonus to his thieving skills. Originally, he would have invented more gadgets as the game went on, but this was sadly scrapped due to lack of development time.
Phoebe from Battleborn is a genius inventor who has created a variety of fantastical tech, a number of which have been inspired by Eldrid tech that seem almost magical in nature. Among her inventions include phasegate tech, which allows her to teleport around the battlefield; her high tech and fashionable Battle Ballgown, which aids her when fighting; and a cybernetic implant which allows her to telekinetically control four of her five rapiers. She's also a skilled roboticist, having been the brains behind her fellow Battleborn Kid Ultra's original design and purpose.
One of BattleCry's classes — called Gadgeteer, naturally enough — has this as their job.
It's easily overlooked given who he is, but Scooter qualifies. To quote Angel: "He may be missing a few chromosomes, but he's a savant when it comes to vehicles."
Gadgeteering exists as a power set in Champions Online. One of the abilities is an "Experimental Ray" which has a chance for various effects, including turning the target into a teddy bear.
Lucca in Chrono Trigger. She resides in a more-or-less modern kingdom with swords and medieval aesthetics, yet she is able to build a fully functioning teleporter, and when the party comes across a robot from the year 2300 she has little trouble fixing him up.
Gary the Gadget Guy from Club Penguin, in case the name doesn't make it obvious. He's responsible for most, if not all of the technology on the island, as well as all the PSA and EPF technology.
Billy Blaze, alias Commander Keen, from id Software's Commander Keen series. Commander Keen built a spaceship in his garden, made from old soup cans, a joystick, a car battery, a vacuum cleaner, and a bottle of Everclear.
Max from Dark Chronicle can make items out of pretty much anything he sees. He just needs to capture photos for inspiration.
The Combo Weapon mechanic in Dead Rising 2 and 3 turns the protagonists into this, being able to MacGyver weapons out of whatever random crap they can find, including boxing glove claws, water gun flamethrowers, crossbows armed with exploding firework rockets, and even a fully functional lightsaber. Nick from 3 takes this even further by being able to build Combo Weapons on the spot without needing a workbench, and even build combo vehicles.
Devil May Cry 5 introduces Nico, a former gunsmith and the mechanic partner (and driver) of Nero responsible for the Devil Breaker system. Some of these arms are simple, like the Overture, which simply lets out electric blasts, and the Rawhide, which is a chain whip that can improve his Wire Snatch, but some can give Nero a Rocket Punch that he can ride on or abilities like turning his pistol into a railgun or even slowing down time itself. Not that surprising for her as she uses pieces of defeated demons to make these for Nero. She also gives Dante Dr. Faust, a literal magic hat that she made based on her father's research that uses red orbs as ammunition.
And on the topic of Nico's father, who was he? Agnus from Devil May Cry 4, who was also an example of this trope in the employ of the Order of the Sword. Agnus created several artificial demons by bringing inanimate weapons and armor to life to serve the Order's objectives, including the Cutlass, Gladius, Basilisk, and the Bianco and Alto Angelos.
In Dicey Dungeons, the Inventor can turn her equipment into gadgets which can be used for free each turn. The downside? She has to make a new gadget after each fight, which means you're constantly throwing away your items.
Jeff Andonuts of EarthBound (1994). He's capable of using laser guns, bombs, and the like, and can turn various broken irons, antennas, harmonicas, and the like into powerful weapons and battle items overnight. And did we mention that he's only thirteen years old?
Eagle Eye Mysteries: Word of God says that Jennifer Eagle's character was created specifically for her to be this. In-game, she built the Eagle Eye Detective Agency's TRAVIS hand-held computer, and is rather picky about who gets to wield it (only Eagle Eye members have the privilege).
The Sole Survivor in Fallout 4 can strip everyday household items like alarm clocks, silverware, or board games for raw materials, which can then be used to make turrets, generators, computers, and modifications for weapons, armor, and even power armor. With the Automatron DLC, they can even use raw materials to build their own army of Mecha-Mooks.
If a character in any Final Fantasy game is called Cid, two things are almost certain: 1) He's a Gadgeteer Genius and 2) his specialty will be Airships. For example:
Never seen, but Cid of the Lufaine in Final Fantasy (at least all its remakes) was the inventor of the first airship.
The very first Cid appears in Final Fantasy II, who offers taxi service with his airship to the heroes. He also gives them advice on how to stop the Empire's Dreadnaught.
Final Fantasy V's Cid Previa builds airships, surprise surprise, and makes Crystal Power Enhancing... Thingies. His grandson, Mid, might represent this trope even more.
Cid Del Norte Marquez from Final Fantasy VI oddly enough doesn't work with Airships, but is no less of a Gadgeteer Genius, seeing as he invented Magitek and designs Powered Armor, weapons, and even pseudo-genetic engineering. However, if you go out of your way to visit the crashed Blackjack after Terra and Locke leave Vector on the way to the Crescent Island, you can find Cid on board offering to help Setzer repair it, claiming that he has some prior experience with airships. Setzer politely turns him down.
Cid Highwind of Final Fantasy VII fame is probably the most well known on this list. He does the same in the Kingdom Hearts games, except he doesn't fight. Or smoke (he gets a toothpick). Or swear.
Cid Kramer of Final Fantasy VIII put up part of the money used to rebuild the mass people mover that would eventually become Balamb Garden (the rest comes from The Mafia, which causes problems later on), which functions as the party's primary mode of transportation early in the story, and negotiates with a city of engineers to help actually create it to his specifications.
Final Fantasy X's Cid. He builds airships and he's loud and boisterous. He doesn't really bring anything new to the table.
Final Fantasy XI's Cid is, fittingly enough, the most prominent engineer and inventor in Vana'diel.
Final Fantasy XII's Cidolfus Demen Bunansa (Dr. Cid for short) is the first Cid to actually feature as a fully fledged villain, being the Mad Scientist responsible for most of the airships and weapons built for the Archadian Empire.
Final Fantasy XIV's Cid Garlond defected from the evil Garlean Empire, shedding his "nan" honorific in the process. Pureblood Garleans, like Cid, are incapable of using magic, but his family was credited with making some of the first airships. After emigrating to Eorzea, which is largely pre-industrial, Cid brings a wealth of Garlean technological expertise, triggering a steampunk/aetherpunk industrial revolution.
Final Fantasy XV's Cindy (Grandpa Cid retired). She's an attractive Wrench Wench who works on the gang's car... which can equip a jet transformation mod.
Final Fantasy XVI's Cidolfus Telamon is a revolutionary first and foremost, but he and his daughter Midadol both have a certain knack for using Fallen technology, able to attach jet engines to a galleon and create a brand new type of ship.
Edgar from Final Fantasy VI designed many of the machines used and exported by his kingdom, including the weapons he uses in battle, most infamously his giant chainsaw. His Job class is described as "Machinist" and, where everyone else is wielding swords, knives, or staffs, Edgar is the only one holding a huge gun.
From Final Fantasy X, Cid's daughter Rikku counts as well, with her "Mix" Overdrive. Both of them are Al Bhed, which are exceptionally technologically advanced, the rest of the game world having been Luddites until shortly before the beginning of Final Fantasy X-2.
The Machinist job in Final Fantasy XIV uses a firearm in conjunction with a waist-mounted aetherotransformer which holds special ammunition, a wrench for Dismantle and Reassemble skills, a stash of grenades, and their foldable Attack Drones.
Frogger's Journey: The Forgotten Relic: Dusty is Kabohti's local mechanic, and helps Frogger by repairing OPART and upgrading it by attaching the other Relics he finds. Impressive, given that it's a long-lost ancient technology.
The whole of the Engineer class from Guild Wars focuses on the use of inventive gadgets to fit multiple situations — you quickly forget that you're limited to pistols, rifles, and shields as conventional weapons when you start using flamethrowers, turrets, grenades bombs, and wrenches as class-specific weapon kits.
The Vances from Half-Life 2. Eli built a robotic dog for his daughter, Alyx. Over the years, she upgraded Dog into a super-strong, semi-sentient Lightning Bruiser.
Monty from Kindergarten is, in his own words, pretty handy with gadgets. He's able to modify a voice-controlled bomb into being remote controlled instead, and the wheelchair he's been confined to in Kindergarten 2 has a laser cannon that he knows how to modify and most likely put in himself to begin with.
Victoria Van Bathysphere from LittleBigPlanet 2. The later portion of her level is an Eternal Engine and she made a robot army.
Bernard from the Maniac Mansion fangame Maniac Mansion Mania. He even invented a wheel that never stops rolling. And it can be used as a power source!
Carl, your chief engineer in MechWarrior 4, has a reputation as one. The saying goes, "Give Carl a hundred tons of steel wool and he'll knit you an Atlas overnight."
While Dr. Wily from the original series has a tendency to use others' robots for his evil schemes, both his constant fortresses and his own line of robots proves that he can back up his intellect. Some games show that Wily can be particularly resourceful: In Mega Man: Powered Up, Wily was able to quickly rebuild his Wily Machine after the first phase and Turbo Man from Mega Man 7 is said in character bios to be the result of Wily repurposing his old car.
Mega Man Legends: Found some old broken drill or toy laser sword? Take it to Roll and she'll figure out how to make a new weapon out of it!
Tron Bonne is her equal. Tron handles the many mechas and airships that the Bonne family use and she is said to have created the Servbots: small robot Mooks who she treats like her children. By the time of The Misadventures of Tron Bonne, she's built 50 of them.
Ciel from Mega Man Zero. And Roll seems like an amateur compared to her. Her accomplishments? Creating a perfect replica of X (Cain certainly couldn't, partially why mavericks exist), creating an energy system to solve the energy crisis that is not only effective but just beautiful (take a look at the reactor of the Guardian airship from ZX!), and making Biometals to match Master Albert's, but also adding the dual Mega-Merge feature. And she created Copy-X when she was nine years old.
Deus Diablo in The Nameless Mod. He built an inanimate object with the powers of a board admin, something Gamespy couldn't do, hence why he was kidnapped.
Conduits in Nexus Clash are supernaturally good at crafting, tinkering, and alchemy, to the point that (with the favor of the Random Number God) it's entirely possible for a Conduit to craft something and find all of their materials still intact and unused on the workbench afterwards. People who think too hard about how impossible that is tend not to become Conduits.
Junkrat from Overwatch. He may be a twitchy criminal with a penchant for explosions, but the guy managed to craft up some impressive weaponry. His grenade launcher, remote concussive mine, and springtrap are all his creations, along with his incredibly powerful Riptire. There's even a good chance that his artificial hand and leg are hand crafted.
Barik is a dwarf who is known by the title of Master Mechanic. He was one of the key engineers of the crystal-powered technology spreading through the Realm. Since then, his signature contributions have appeared in almost every field and vocation, from mechanized mining suits and rocket-powered wings to the crystalline weapons used by Magistrate and Resistance soldiers alike.
Ruckus is a tiny goblin who fights in a Mini-Mecha that he repurposed from a mining mech. To increase his mech's power, he installed a crystal that was actually the mind-stone of a war golem. This mind-stone now uses the mech suit as his new body and is now partners with Ruckus under his new name, Bolt.
This trait seems to be the hat of most electric type specialists. With the exception of Elesa due to being a model, Lt. Surge, Watson, Volkner, and Clemont had a huge hand in setting up the complex design mechanisms for their gyms for one reason or another, and Sophocles constructs a device that's integral to his Island Trial.
Many operators in Rainbow Six Siege have engineering degrees and develop their own specialized equipment. Examples include explosive traps, signal jammers, sensors that detect people or electronics through walls, a drone with a mounted taser, and a breaching device that can punch a hole in a wall and launch several grenades through it.
The Lombaxes from Ratchet & Clank are an entire race of Gadgeteer Geniuses. Ratchet himself was able to build a functioning space ship out of A BOX OF SCRAPS! spare parts IN A CAVE! on Veldin simply by following Gadgetron's voice prompts (not to mention the list of his wacky inventions that Clank rattled off), and the Lombax Secret is in fact an inter-dimensional portal device. According to the Smuggler, Lombaxes can't leave any invention the way they found it and are forever tinkering.
Lucas Baker from Resident Evil 7 is a truly evil example. He's able to make all different kinds of devices of torture for the sick games he plays with his victims, and he does it all under his family's nose.
In Roots of Pacha, Garrek is the resident thinker who comes up with new ideas for inventions to contribute to the village. The others, particularly Grob, are slow to warm up to his technology, but they eventually accept it.
Li Kohran from Sakura Wars, though the stuff she makes also has a tendency to randomly explode.
Episode 2 of Scooby-Doo! First Frights has Mystery, Inc. encounter Numbers, a boy who invents gadgets to try and track down the culprit behind the toy army at the carnival.
Bentley is a techno genius who even fitted his wheelchair with gadgets.
His ex-girlfriend Penelope is one as well, albeit a villainous example. She's more specifically focused on RC technology, having made for example a remote-controlled car with a turret mounted to it.
Solatorobo has Merveille, who is credited with single-handedly raising the bar for Kurvasz Mini-Mecha design. She's also quite skilled in biology, Creating Life while barely old enough to be out of high school.
Dr. Eggman is capable of building entire robot armies and armadas of airships in what can't be more than a few weeks or months. His creations also appear to have well-nigh-unlimited power, fuel, and ammunition, as well as effectively healing technology on several examples.
Marina from Splatoon 2 is quite an enthusiast regarding machines, as her stage intro dialogue shows. She even creates a new Shifty Station stage for each Splatfest, using advanced Octarian technology. The Octo Expansion reveals that she was actually a top combat engineer for the Octarians before her Heel–Face Turn, having graduated from her elementary training at the age of nine.
Area from Street Fighter EX2 Plus. While she's not given much of a story, it's mentioned that she's a greater inventor than her father.
Professor Doctor is not only the brains behind the De-Dizzler 3000, which cures the Dizzies of their condition, but also your source for ambulance upgrades.
Captain Brains is a villainous example, having the technology behind the Dizzying pandemic in the first place.
Subverse has two alien examples: Dallick, a diminutive stoner who nonetheless is a genius mechanic, especially for ships and advanced electronics, and Taron, a Cat Girl "nikith" who aside from being an extremely skilled and acrobatic huntress also has an incredible love and talent for technology, able to invent a set of highly-advanced, custom-made burglar's tools that let her bypass any sort of known security system in the Prodigium galaxy.
The sixth boss of Paper Mario 64, Huff N. Puff, built the Puff-Puff Machine, which was used to block out the sun in Flower Fields, as well as block the entrance to his cloudy lair.
Bowser Jr. varies: He definitely loves to use mechas to fight Mario, ranging from giant robots to his his Junior Clown Car, but some games imply these to be presents from his father or built by other Koopa Troop members while others imply that he takes a more active role in designing them. Bowser Jr.'s Journey in particular sees him modify Iggy's faceless Clown Car into a replica of his Junior Clown Car.
Wario himself is surprisingly this, considering that in Wario: Master of Disguise, he's able to create a device that allows him to go in and out of his television at will. He is also shown to create other devices in the WarioWare series as well.
Captain Syrup in Wario Land II. All the boss fights against her involve knocking her out of various hovering vehicles that sport various weapons, and one fight sees her remotely controlling a robotic Spear Man.
Little Mad Scientist girl Penny Crygor from WarioWare: Smooth Moves fits the trope to the letter. She's also totally adorable. Her story in Smooth Moves has her participate in an "Invent-Off" against her granddad Dr. Crygor, who is a Mad Scientist himself, and she wins. In WarioWare: Get It Together!, she uses a water jetpack she made herself to move around.
The Engineer of Team Fortress 2 is capable of creating NASA-level sentry turrets and teleportation devices using nothing more than his wrench and scrap metal collected from weapons dropped by the recently dead. There's also his laws-of-thermodynamics-be-damned dispenser, and the fact that he can make one from scratch using things such as a wooden baseball bat, an empty glass bottle, or a glass jar filled with urine. He's also the person who invented it. In the 60s. Then again, he does have 11 PhDs, so it's a little justified. He also built himself a robotic hand to replace his missing right hand. A hand that he cut off so he could replace it with a robotic hand.
Rika managed to build, arm, and pilot at least three separate tanks designs in a setting devoid of the industrial-grade machinery usually required to construct one.
The Gadgeteer is the name of a class in Twilight Heroes — they make many of the gadgets and devices that they use in combat.
Puck of Vanguard Bandits is capable of repairing the strongest and oldest ATACs in record time and can keep them in working order with the smallest of resources. Taken to extreme levels, as he proves that he is fully capable of making an ATAC even stronger than the one legends portrayed as strongest using only scrap parts of a broken machine and a weaker power source. Takes a dark twist at the end of the "Ruin" path, when he improves Zulwarn's efficiency. It only needs a few drops of blood instead of a mass human sacrifice to power it, though it still corrupts people.
The Gadgeteer is an actual class in Wizardry 8, and it's just as powerful as you'd expect. Thankfully the rarity of components means that you can't really have more than one in the party, which keeps the game from becoming unbalanced. The only gadgeteer in-game if you don't make one in your party is a trynnie named Madras, who calls himself a gadgeteer by name.
This trope is the defining characteristic of both Gnomes (Alliance) and Goblins (Horde). Gnomish tinkerers are famous for inventing bizarre (if not reality-warping) inventions including (but not limited to) helicopters, robot chickens, teleporters, mind control helmets, and even world shrinkers. Goblins on the other hand tend to love explosives of all kinds and are master bombmakers, rocketeers, and sappers; but also make lumber-harvesting robots, airships, and motorcycles. Although generally on opposite factions, Gnomes and Goblins have a friendly rivalry and often cooperate on complex engineering tasks and love to compete in racing.
Players of any race can take the "Engineering" profession, which allows them to embody this trope, but Gnomes have a racial bonus to Engineering (Goblins have a racial bonus to Alchemy). The profession even allows the player to create Mad Scientist-style goggles and to make unique modifications to their armor, such as parachute cloaks and rocket boots. Although true to Gnomish and Goblin tradition, player-made inventions have a nasty tendency to backfire through explosions, accidental size modification, poultryfication, and teleporting you far above the ground. If it does not do any of this it is either a bomb, has a massive cooldown time, or is a robot or something that works once before breaking.
