As it is known, Humongous Mecha tend to be made of some sort of Unobtainium that's better than the alloys we have even today. Given what they have to face (Kaiju, other mechas, giant spaceships), this is natural.
And then there are these robots.
As the trope name implies, they're made of scrap metal or otherwise relatively cheap materials.
Naturally, this means they'll be more fragile than conventional Humongous Mecha, and depending on the setting, they are either Joke Characters or simply low-tiered, yet there can be events that lead to them being surprisingly more valuable than one would assume a robot of their make to be.
Anime and Manga
- Mazinger Z has Boss making his own mecha named Boss Borot out of parts from the scrap heap. Predictably, as a Plucky Comic Relief character, Boss Borot was broken more easily than even Sayaka's Aphrodite/Diana A. And being made of scrap metal, he obviously could not have any of the special weapons Mazinger Z has. That said, it still had enough strength to pull the two aforementioned mechas out of a pit hole, squash Iron Cross tanks, and even toss a few Robobeasts around. As for going out in space, given its open air "cockpit", this only means the pilots have to wear space suits.
Film - Animated
- Transformers: The Movie has the Junkions, who are like Transformers but native to Junkion/Planet Junk rather than to Cybertron and are made out of junk themselves. This makes them easy to break, but they can simply pull their pieces back together and keep going.
Film - Live Action
- The Adventures of Sharkboy and Lavagirl, in the real world, Tobor is a humble little "robot" made by Max from scrap parts. In Planet Drool (a place "made" from Max's dreams), he's sort of "translated" into this, though stuck in the Dream Graveyard as one of Max's discarded dreams, and unable to move at all... except for (as Sharkboy points out) his eyes and mouth, which he uses to transport Max and his friends for a while.
- Pacific Rim: Uprising: Being built from literal scrap metal, some car parts, rusty construction equipment, etc., the Mini-Mecha "Scrapper" counts as this. Well, it's two stories high, but it barely reaches the shin of any other standard Jaeger. But it's no less a badass than its bigger kin, and even contributes greatly in the finale.
- The goofy Martian robot in Santa Claus Conquers the Martians certainly looks like it's made of scrap materials.
- Ultraman 80: The monster Gazera is a giant robot made of scraps and various spare parts. Originally a homemade toy made by a lonely child, said toy was affected by Minus Energy and comes to life before transforming into a massive kaiju.
- Ultraman Z: King Joe STORAGE CUSTOM, one of the Mechas developed by STORAGE, which is made from salvaged parts of the destroyed King Joe and existing STORAGE technology, making it the first version of King Joe in the series on the side of the good guys.
- BattleTech: On poor planets like many Periphery worlds, it's very common to see Battlemechs that haven't been given routine mantainence in decades or even centuries. Enterprising mechanics can keep them in something resembling working order, but they tend to be a mishmash of parts, many of which don't function correctly (if at all). The absolute worst of these tend to be so-called Frankenmechs, which as the name suggests are when multiple different mechs are crudely stuck together. On very rare occasions, the stars align and a Frankenmech ends up being a deadly war machine. Most of the time, it struggles to move under its own power without falling to pieces and should not be subjected to actual combat by anyone lacking a death wish. During the devastation of the Succession Wars, such mechs became widespread as mech factories were destroyed and it became very difficult for anyone to keep a mech in working order. But with mech production ramped up during the 4th Succession War, such things are typically only found in the poorest of planets.
- Warhammer 40,000: As with most of the vehicles that they make themselves, the large walkers used by the Orks, such as Stompas and Gargants, are constructed from a mishmash of scrap, stolen technology and guns. Constructed as idols to their barbaric gods as much as weapons, these enormous, vaguely ork-shaped monstrosities often look like walking junkyards with weapons fitted almost at random across its superstructure. Despite their incredibly crude look, these ramshackle war machines are incredibly durable, sporting thick armour plates and a rugged design that allows them to continue attacking even if large chunks have been blown off. Due to their lower level of technology, the Steam Gargants built by the Feral Orks tend to look even more ramshackle and typically have tracks rather than legs as they lack the skills to make a true walker.
- In Breath of Death VII, a giant robot made of junk, named Junk Monster, is fought as one of the bosses in the game. It was built to recover the eight crystals to use them to power the time machine so the apocalypse would be prevented, but it was reprogrammed by evil forces to destroy the heroes instead.
- Cuphead: Mad scientist Dr. Kahl and his giant scrap-metal robot are one of the many bosses in the game. The battle takes place in a huge scrapyard, presumably where the robot was built.
- As a Mazinger Z character, Boss Borot also appears in the Super Robot Wars franchise. He's certainly a low-tiered mecha compared to everything else, and to reflect his material cost, it only takes 10 credits to repair compared to the usual few thousand credits needed for everyone else's mechas. That said, with the right parts to slot in (up to four), having three pilots (Boss, Nuke, and Mucha) and a great set of Spirit Commands between them, he's a surprisingly good unit to field. Just make sure to keep him away from too much enemy fire.
- Mega Man: Junk Man and his Mega Man Battle Network counterpart, Junkman.exe are both this, though JunkMan.EXE is actually a program, not a robot. Plenty of Fortress bosses also have this aesthetic, such as the Guts Dozer.
- Sonic the Hedgehog 4: In Episode II, the boss of the Oil Desert Zone is a giant mecha made of scrap, built by Dr. Eggman.
- Tech Romancer: Magical Girl Pollin pilots the "Magical Patched Robot Bolon," possibly a reference to Boss Borot above. It's cobbled together from a bunch of random items, with a bus and a boat for feet, a water tank for a body, a house for a head, and a wrecking ball and power shovel for arms.
- The Hollow: In season 2, Olym is giant mecha that lives in a junkyard and is made out of junk. He acts as the Final Boss of that season and is almost indestructible. "Helping" its case here is the fact that it's not fighting other giant robots but a bunch of kids.
- Megas XLR:
- The eponymous mecha is a downplayed example. While most of it was technically found in a scrap yard, it's tech from the future, and the only modern scrap parts are the cockpit and various other things Coop used to get it running again.
- The junk dealer Goat eventually decides to get his own giant robot (whom he names Darlene) cobbled together from junk—which promptly falls apart.
- The Little Rascals: In "Science Fair and Foul", Buckwheat builds one from an old TV set, some tin cans and other found components.
- Looney Tunes: In The Solid Tin Coyote, Wile E. Coyote builds a giant robot coyote out of spare parts from a junkyard.
- In the Steven Universe episode "Back to the Barn", Peridot and Pearl prove their engineering skills with Mini-Mecha they rapidly built out of scrap in the barn◊. Pearl's has a cockpit made from airplane parts left behind by Greg's aunt and uncle plus a traffic cone nose. Part of the arms of Peridot's mech are made of tires and hazard signs.
- An episode of Godzilla: The Series had a mechanical monster that started off as a small machine that assimilated more and more machine parts.