Crabs.
They've got big pincers. They've got googly eyes. They've got a thick exoskeleton. They've got a funny sideways walk. In some parts of the world, they make delicious meals.
But what happens when you decide to enlarge one? You get a scary-looking monster fit for a Boss Battle. And possibly an extra-large delicious meal if you decide to cook it afterward.
Like Big Creepy Crawlies, insufficient oxygen use renders the truly huge ones impossible. Real life crustaceans are docile because of energy issues, so even if did work out, expect them to be docile.
According to Sony, Giant Enemy Crabs appeared in "famous battles that actually took place in ancient Japan". When encountering one, you may Attack Its Weak PointFor Massive Damage, while using Real Time Weapon Change.
See Sea Monster for other monsters from the deep. Often similar to a Giant Spider, but not quite as creepy (and theoretically tasty). A mechanical Giant Enemy Crab would be a form of Spider Tank.
Harima takes on a Giant Enemy Crab in School Rumble in the middle of a search for cooking ingredients, and kills it offscreen with a trident. The anime exaggerated its size so that it towered over him.
The Radham Beasts (called Spider-Crabs in the dub) of Tekkaman Blade.
A crab larger than the trees of the jungle she fell into chases Chisame in Mahou Sensei Negima! at the start of the Magic World Story Arc.
In episode 4 of Tears To Tiara, the main characters accidentally call out an entire beach's worth of Giant Enemy Crabs. Since the hunting party has among their number two Badass Normal warriors, a Staff Chick, an Old Master cleric, and a resurrected demon king, the crabs still get slaughtered. The party celebrates with crab hot pot, using the crabs' shells as cooking pots.
Hitagi Senjogahara from Bakemonogatari starts out the series possessed by a Giant Enemy Crab. This leads Oshino to point out the real reason why Giant Enemy Crabs aren't to be messed with. They're hard to eat.
Bleach anime episode #205. At the end, all of the spiritual energy being released in the kemari game summons a giant crab-like hollow. After Uryu and Chad attack it, Ichigo kills it with a single blow.
Roger Corman's immortal Attack of the Crab Monsters — People are trapped on a shrinking island by intelligent, brain-eating giant crabs. Not only were they big crabs, they could imitate people's voices.
In the Toho film Space Amoeba, the titular alien takes control of a crab named Ganimes and enlarges it.
Garthim, (which are only vaguely crab-like) from The Dark Crystal.
Pinocchio in Outer Space. On the surface of Mars the title character finds animals made gigantic by atomic mutation, including huge crabs with fangs◊.
Godzilla enemy Destroyah is made of thousands of these - which are already giant by themselves.
Filipino boxer Manny Pacquiao fights one of these in Wapakman.
Literature
The titular Prador from Neal Asher's Prador Moon.
Larry Niven's Beowulf's Children introduces the Scribe, which resembles a giant land-dwelling horseshoe crab. Fortunately, they're also Gentle Giants...with defenses that deter all potential predators, even the grendels and the huge flesh-eating "bees" with Super Speed. To get a feel for how big they are, note that the colonists name the first Scribe they meet "Asia".
Guy N. Smith wrote a series of low-rent horror novels in which giant killer crabs run scuttle amok.
Wall Around a Star has the glassy crabs grown by the Cuckoo cultists on Earth as well as found naturally on Cuckoo itself (if anything there can be described as natural).
When you're a mouse, all Crabs are Giant. Case in point: In Mossflower, the Salamandastron Quartet end up having to get past a Mama Crab that's bigger than Chibb.
In H. G. Wells' novel The Time Machine, the Time Traveler encounters some rather menacing giant crabs on his way to the end of the world.
From Harry Potter and the Goblet of Fire, Hagrid's infamous Blast-Ended Skrewts, a hybrid between Manticores and Fire-crabs. They start out as being merely a poor choice of a Care of Magical Creature class project, but fully mature they become so distinctly sinister and dangerous that they are employed for the Third Triwizards Champions task.
In John Dies at the End, a gorilla riding a giant crab (or possibly a single creature resembling a gorilla riding a giant crab) violently escapes from a chemical plant that makes drain cleaner. No, it doesn't make sense in context, that's the whole point.
There's also the memorable Crushtaceon from the novel Nuklear Age.
Terry Brooks took one of these, and added tentacles to it in The Sword of Shannara. Later revisions added metal plating to them. And created multiples.
Dr. No had Honey Rider tied down on the shoreline ostensibly to be eaten by a swarm of crabs, but more likely to scare her to death. However, she knew her sea life and knew them to be harmless, so she calmly let them march over her.
In The Beyonders, the first word fragment is unintentionally guarded by a giant crab. Originally it was guarded by a hermit; the crab moved in on her own. She's terrifyingly fast as well as Nigh Invulnerable, and escaping her is a chore and a half for the protagonists.
The Doctor Who serial The Macra Terror is about a society menaced and brainwashed by creatures that look like giant crabs. Really low-production-value ones.
The Macra returned in CGI form the new series episode "Gridlock".
While not actual crabs, the Shadows of Babylon 5 have enormous black spaceships called Battlecrabs. Living Ships, at that, with a memorable psychic scream (not without reason) and they can cut through pretty much any other warships like soft cheese.
In module S2 White Plume Mountain, the PCs could fight a giant crab in a air bubble inside an area filled with boiling hot water. An illustration from the module◊.
The Far Corners of the World brings the Monstrous Crab, better known as That Damn Crab for it's tendency to grapple party members and drag them to a watery grave as well as its insane damage output, high AC, and mindless immunity to illusions. It's listed as an appropriate encounter for 3rd level parties and is generally considered a match for 7th level parties and a total TPK machine if used as it's printed.
The monster was also reprinted with only minor tweaks in Stormwrack and given cousins of all sizes. The book also adds the Hammerclaw, which is a lobster with all the same strengths plus the ability to hide in coral/rocks and to stun the party with an at-will sonic attack for the same CR.
The first issue of Pathfinder Chronicles features a giant hermit crab that uses a giant's helmet as its shell.
Eclipse Phase features Novacrab pod-morphs, vat-grown cyber-crabs that may be player characters. Due to the setting's ubiquitous Brain Uploading, players can select a novacrab body as well, providing a huge bonus to strength and able to survive in just about any environment.
Steel Shell Crabs are a unit for the Tritons in Monsterpocalypse. Also, the Crustaceor Lobstroyer monster.
While not strictly a Crab per se, Old One Eye and most Tyranid Monstrous creatures in Warhammer 40K can take Crushing Claws, which are described as crab-like. Being Monstrous creatures, they are quite large.
Interestingly, the massive damage part out-meme'd the historical accuracy of giant crabs.
There was a mod for the standard Headcrab in Garry's Mod that made it near-impossible to kill, screamed like Godzilla and devoured anything within seconds of it getting in range. It could be taken down with SEVENTEEN simultaneous rockets, something that could potentially crash the server.
The mud crabs in The Elder Scrolls setting are rather large for the species. Also, Oblivion includes a literal giant crab as an Easter Egg enemy, although this is a coincidence since the game came out before the Genji incident.
Morrowind also features a crab shell large enough to contain an entire district of one town. The "Emperor Crab" species it came from, however, is stated to be extinct.
Semi-official word from the writers says that the Emperor Crab was resurrected to battle a massive Daedric invasion during the events of Oblivion. We never see it though, as we're stuck in Cyrodil. I suppose this would be a case of a Giant Friendly Crab though.
Morrowind's Mudcrab Merchant subverts the enemy part of the trope. It looks the same as any other mudcrab (and has the same in-game name), but instead of being hostile it is a merchant, with the most gold in the game.
One quest in Skyrim pits you against a giant Mudcrab ghost.
The 3rd Metal Slug has several of these in the first level ranging from man-sized creatures to a giant boss with cannons strapped to its back.
Katamari Damacy. The first game even has a level ("Make Cancer") devoted solely to rolling up crabs. And yes, the coconut crab is one of the types to be rolled up.
The boss of River Belle Path in Final Fantasy Crystal Chronicles is a nasty old crab with numerous weapons sticking out of its body from past battles. It reappears in the same position in Ring of Fates.
A giant fiend in the shape of a crab-like spider is the boss of the first dungeon in Final Fantasy X 2. A palette swapped version appears in Via Infinito.
Vagrant Story had an entire family of palette swapped crabs, named "Iron Crab", "Giant Crab", and "Damascus Crab".
Cool Spot toys with this: its crabs are regular-sized, but they're quite big from the viewpoint of the player character, the spot from the logo on a 7-Up bottle.
Ecco The Dolphin has to face many Small Enemy Crabs along with the giant ones. There's actually an implied explanation for this at the end of Tides of Time; the Vortex ended up becoming the ancestors of arthropods, so it may be that these creatures hate Ecco due to species memories.
One of the units the Sai in the game Stormrise have access to is the Matriarch, a giant, genetically engineered crab that has mouths on its pincers, can spawn smaller crabs called broodlings and can shoot acid over large distances.
Cancer Bubble has also a slight subversion to him, in that, while much larger than your average crab, he's the absolute smallest of all the bosses (then again, his human half, Claude Pincer, is only in third grade).
Mirelurk meat is also one of the better foods in the game, healing a large amount of health. Mirelurk cakes are a popular snack among wastelanders.
Without a doubt, the most awesome food resource in Civilization IV is the crabs. Zoom in on them, and watch them wave their pincers at each other as though in animated discussion...
There's a lot of crabs in various beaches in World of Warcraft, ranging from normal sized to big to a few giant ones.
Notably, in the Wrath of the Lich King expansion there is a Giant Friendly Crab as a quest-giver. Considering Blizzard's tendency to include ShoutOuts and IncrediblyLamePuns as Easter Eggs in their games, it's certainly possible this is a reference.
Monster Hunter has approximately six different flavours of Giant Enemy Crab in its latest incarnation — two small ones ("small" being about twice human size), three large ones ("large" being about the size of a truck), and one absolutely huge one. Oh, and you fight them on foot, with approximately medieval-age weaponry.
Monster Hunter Freedom Unite even has a mission called "the giant enemy crab".
Recurring Boss Full Metal Hagger in the World Of Mana series. Usually fought near the beginning of the game.
A giant crab spawning normal-sized crabs has to be fought in the adventure game Bargon Attack.
Star Fox Command's Fichina stage has you fight against the thought-to-be-dead Andrew Oikonny, who battles you in a mech called the "Death Crab." You shoot off its legs, then its face for mass...oh forget it.
The original Star Fox has large mechanical crab enemies on Titania.
Fraxy has the Original Cancer and the Giant. Enemy. Crab.
Resident Evil 5 has you fight the U8 in an elevator shaft. Given Umbrella's penchant for using animal test subjects as B.O.W.'s, it's no wonder you'd have to fight a giant mutated crab at some point.
God Hand, at one point, features a fight between Gene and a Giant Enemy Crane (complete with pincers). Also, the entirety of the game's fourth world takes place on a Giant Robot Crab.
God Hand even makes further references to this meme: one of the Chihuahuas in the Chihuahua Races is named "Massive Damage".
The RTS Krush, Kill 'n' Destroy (KKnD) had the Evolved faction, who could train giant beasts to fight for them in place of armoured tanks. One of their largest units is a giant crab with a missile launcher strapped to its back.
As well as the first and third bosses in its Enhanced Remake, Blaster Master Overdrive.
The toughest beast that Nero Chaos in Tsukihime possesses is some sort of crab spider thing that is larger than an elephant. Presumably, it's tougher than the dragon he had used before, but it doesn't matter much when your opponent kills everything in one hit regardless of anything like armor or actually damaging you.
The last level in the arcade shmup Strikers 1945 featured giant robot alien crabs as enemies.
Patapon features two crab bosses named Cioking and Ciokina. You get to cook them.
Recently, with the "Secret Armory of General Knoxx" DLC, the secret final boss (who is pointed out with signs saying "SECRET FINAL BOSS THIS WAY" from the Second area of the DLC) is Crawmerax, a Giant Giant Enemy Crab whose level is always three levels higher than the game's current level cap.
And who can only be hurt at all by hitting its weak points.
Brave Story: A New Traveler has a Giant Enemy Conch named "Boogaboo Crab" in the Seaside Cave. It has trees growing out of the moss on its shell and the 'crab' goes "BOOGA-BOOGA-BOOGA-BOO."
Parasite Eve has a giant crab boss in the warehouse.
The third boss of Pirates: The Legend of Black Kat is a giant crab. And yes, the trick to beating it is by flipping it over onto its back and...well, you getthe idea.
Vega Strike has large friendly crabs, known as Rlaan.
Irukandji's only boss is a giant crab. Even the page for the game calls it a "Giant Enemy Crab."
Titan Quest: Immortal Throne has regular crabs (of beach and swamp variety), and then it has the Giant Karkinos (no prizes for guessing what it is). As with the rest of the game, this has some basis in actual Classical Mythology: according to some variants of the legend, when Heracles was fighting the Hydra, Hera sent the Karkinos to attack his feet while he was otherwise occupied (wrong hero, Hera), to no avail - but on its death, she placed it in the stars as a constellation. Which means... yes, Heracles beat Cancer.
Umihara Kawase features one as the boss of field 56. It's one of the more sensemaking enemies in the game.
In Monster Rancher 2, if you send your monster on Skill (accuracy) Errantry and it makes it to the final segment, it will have to "fight" a giant crab by throwing coconuts at it. If it fails, the crab will squash your monster into a pancake, adding a comical element to the training (as though everything else about the special training wasn't already laughable; fighting off sharks on a mere wooden raft? Really?)
Brave Soul gives us the Giant Enemy Fire-Breathing Crab!
X-Scape on DSiWare (made by the same company who made Star Fox Command and the director of the original Star Fox, both of which incidentally had Giant Enemy Crabs of their own) has a so-called "ancient" weapon called the Gigacrab, referred to in the Quest menu specifically as a giant enemy crab.
From the world of Pokémon, we have a subversion in the Kingler species. Unlike most other examples on this page, you can actually recruit Krabbys and Kinglers to fight for you as part of your team. Several other species of crustacean also apply, under the Video Games heading below...
Kirby 64 The Crystal Shards features a Slightly Larger Than Average Enemy Crab as a boss battle. There's also regular-sized crabs for Kirby to munch on.
League of Legends features an alternate skin for their quadra-pedal undead cyborg Urgot called "Giant Enemy Crabgot." He fires his claw at his enemies.
Banjo-Kazooie had you fighting a giant hermit crab in order to obtain the jiggy inside its shell.
In Age Of Mythology playing the Greeks you can get access to a giant crab unit called the Carcinos with the right god.
The mine boss of Wild Guns is a giant robotic crab.
One of the Bosses of Pirates The Legendofthe Black Buccaneer is a giant crab that you (As Francis Blade) can defeat using both hand grenades and the cannon that you used earlier to blow up the bars to get the trinket to turn into the Black Buccaneer.
The sixth boss of Adventure Island III is a large crab wielding an Epic Flail. The second boss of Adventure Island II is large hermit crab.
Alice Madness Returns has a crab equipped with an Arm Cannon. It also outsizes every other creature that appears in its respective chapter. Oh, it is also a Cigar Chomper. Guess what it does with its cigar since its Arm Cannon is of the early Blackpowder-era variety?
Crabocolypse from Commando 2 is a robotic version. You stand on a train when you fight it, while it does a Wall Crawl on the train track support beams.
The Crustacrab and its shell-less, baby variants (who are still as large as Red himself) from Solatorobo. Unlike many of the others on this page, you do not Attack Its Weak PointFor Massive Damage. Instead, you catch the rocks it throws and toss them back to stun it, then steal its shell so you can toss the crab around. There are also even larger hermit crabs who have taken over entire battleships as their shells in the Fishing Minigame.
Chapter 15 of Realms of Ishikaze has one of these as a boss of the Ruins of Amilleo. Arashiko must attack its soft underbelly for massive damage.
In Nodwick, the party meeting a giant crab inspires them to pull out the Crab Cracker + 5, Decanter of Endless Butter and Bibs of Protection.
Fire Slicer from Axe Cop, who after eating a crab, turned into a very tall crab with super-duper sharp claws that could stab bad guys in the heart and pinch.
Karkat's guardian in Homestuck is two-and-a-half out of three. He's definitely giant and he's definitely a crab, but while Karkat does fight him, he's more of a parental figure than an enemy. Played straight, however, when crabdad dies and the comic's Mooks begin to take on his characteristics.
Exosquad had a Neosapien E-frame design styled after crabs, which was admittedly one of the most powerful frames in the show (evident in the fact that Shiva, the best Neosapien General, preferred it to all others). Also, the crablike Neo Warriors were among the nastiest enemies the Terrans encountered.
Rampage of Beast Wars is a Transforming Mecha who chose a crab to transform into. He's also quite a bit larger than most of the other Transformers in the series and something of a sadist.
Also Rampage is near immortal and his only weak point is his spark, which Megatron has split in half so that he can keep Rampage in line by squeezing it and essentially disabling the insane robot
Macrocheira kaempferi, the giant Japanese spider crab, which can reach sizes of up to 12' 6'' across, making it the world's largest crab. It is usually harmless to humans, but a few Japanese fishermen, who catch the crabs for food, have reported it can inflict serious injuries or even kill with its giant claws. GameFAQs and GameSpot users used that animal as an example to prove the trope naming presentation was right, Medieval Japan had giant crabs...
We're all going to be eating our words when palaeontologists find giant crab corpses in ancient Japan. It will be even worse when sword and arrow marks are found on their weak points. The official cause of death would be of massive damage.
That video is nightmare fuel incarnate. Imagine, for a second, that small creatures were able to pry your mouth open so smaller versions of them could go inside and begin feasting on your innards...
Other Crustaceans of Unusual Size
Card Games
In addition to the giant crabs mentioned above, Magic: the Gathering also gave us the Homarids (effectively barely-anthropomorphic lobsters at war with the local merfolk when introduced), some of which were clearly a bit bigger than the others...
The collectible card/model series Pirates Of The Cursed Seas features a number of sea monsters in addition to its ships—amoung them, a handful of giant crabs.
They will constantly question you (dad-a-chick?) while ripping your extremities apart.
The Stormlight Archive has the massive lobster-like creatures known as chasmfiends. They are powerful enough to flatten even somebody wearing the setting's resident MagitechPowered Armor.
The various deadly Lost World life forms of Fragment are distant cousins of mantis shrimp, although they've long since evolved into whole classes, possibly even phyla, of their own.
One of the bizarre inhabitants of Brian Lumley's Lovecraft-pastiche Dreamlands novels is a giant pillbug referred to as "the Running Thing". It's friendly to humans, and is a subterranean predator of various deep-dwelling nasties up to and including dholes.
Live Action Television
Countless ones in Power Rangers, though the most memorable one would be Captain Crayfish from the second season. He even comes with his own crew of Psycho Rangers.
An inversion of the "Enemy" part can be found in the Samurai Gold Ranger's Clawzord; it's a giant mech-lobster.
Monsterpocalypse the Tritons have a monster Crustaceous which is a giant bipedal lobster.
Video Games
Warcraft games have Lobstrocs/Makruras (both names seem to be used interchangeably) and the Bogstrok, which are lobster people. They're about the same size as most other humanoids, making them very large for crustaceans. There's also the truly gigantic Rokmar the Cracker as a boss encounter.
Corphish and Crawdaunt from Pokémon. Anorith and Armaldo are based on ancient ancestors of arthropods, while Kabuto and Kabutops are based on the living fossil that is the Horseshoe Crab. Like the Kingler species (see above), these guys are all subversions, since you can actually recruit them as part of their team and get them to fight for you.
The Blisk from Destroy All Humans!, aliens described by Pox as brutes with large claws who look like the result of a cockroach mating with a lobster.
Claude the Lobster, particularly in Peggle Nights.
Alien Soldier has a large unnamed lobster as a boss that appears in a Big Lipped Alligator Moment. Your character saves a blue teddy bear from kissing aliens. Said teddy bear then decides to help you by driving a power boat to your destination. After fending off its minions, this big crustacean swims up to your boat, grabs the teddy bear andthrows him off the boat, and proceeds to fight you.
Ys: The Ark of Napishtim has Zonplas, a giant bat-winged lobster-type thing.
Super Sonic Blast Man had one as the Level 4 enemy. This one was particularly horrifying since it could crush SSBM to death with its claws even after losing them.
Final Fantasy V had the Karlabos/Cray Claw boss that resembled an lobster/earwig hybrid.
One of these, a lobster, appeared in a special episode of The Penguins of Madagascar during their battle with their arch enemy, the evil dolphin Dr. Blowhole, as a Giant Mook known as....
(With deep dramatic voice) CHROME CLAW.
An episode of The Simpsons was about Homer adopting a lobster in which he named "Pinchy."
Hanna-Barbera's Moby Dick. In the episode "The Crab Creatures", Moby has his tail pinched by a giant crab under the title creatures' control.
Real Life
Giant marine cousins of the pillbugs (a.k.a. rolly-pollies, sowbugs, woodlice) you can probably find eating rotted plant matter in your compost heap are quite common around deep-sea hydrothermal vents.
