Giant Equals Invincible

After generations of Kaiju movies including Godzilla, Gamera and countless imitators, viewers seem conditioned to accept that any giant monster or robot is completely immune to conventional weaponry. This can be a problem for filmmakers, either making the military in their films look stupid for even being there or destroying the audience's Suspension of Disbelief when Five Rounds Rapid actually works. Not much can be done about this.

It would seem that audiences usually like to see a more creative method for destroying the monster than More Dakka.

There are a few methods for overcoming this, including Depleted Phlebotinum Shells and (inexplicably) attaching the very same weapons to another giant robot or monster. On the other hand, simply laying out poisoned bait for these critters and letting their appetites do them in will never, ever, ever occur to anyone.

Anime and Manga

 * Mazinger Z and its sequels (Great Mazinger and UFO Robo Grendizer) played this trope straight. Combat jets, tanks, missiles... could not even scratch the armor of a Robeast, and it could only be defeated by a similarly giant weapon. It is subverted with the FemBots, though, since Aphrodite A, Diana A and Venus A could be easily defeated, and Aphrodite A could be briefly deterred by an army of Mooks using conventional weapons.
 * Of course, this is a staple of the Super Robot Genre, since it justifies the existence of the Humongous Mecha. Since a Robeast can not be defeated through conventional weaponry, it must be fought with another giant enemy. Tetsujin28-Go, the first Humongous Mecha played this trope completely straight. It was intended to be Japan's ultimate weapon during World War II. Since that war was over before the robot was finished, Tetsujin is used to fight mostly criminals and terrorists. Other examples are: Getter Robo (that battled giant cybernetic DINOSAURS), Raideen, Combattler V, Voltes V (it was supported by the army, but conventional weapons were never strong enough to battle Boazanian's Slave Beasts), Daimos, Zambot 3, Daitarn 3...
 * In Tengen Toppa Gurren Lagann, the Humongous Mecha are shown to be vulnerable to concentrated small-arms fire (something that Yoko uses to her advantage on a number of occasions). This hasn't stopped some viewers from asking, "Why are they shooting at the robots when they know it won't do any good?" later on.
 * Neon Genesis Evangelion takes this one seriously. On the one hand, they try bullets, missiles, and clean nukes on the angels; but the reason the Evas exist is that the Angels are protected by a force field (they call it an AT field) that only the Evas can cancel out with their own AT fields. Though there are cases where Science Fiction Based Weapons DO defeat them.
 * The trope is very much averted in Macross for both the Zentradi and their battle pods. While Zentradi (at least those of Bretai's type) are powerful enough to dismember Giant Mecha with their bare hands, human weaponry or Zentradi weapons wielded by humans can take them down in an instant.
 * Giant Robo takes place in a world where 'Experts' have various superpowers and can duke it out with each other, to the detriment of the landscape. But with a title like that, guess where the real force is. The show mostly plays it straight - Giant does equal Invincible, unless you're prepared to die soon afterwards.
 * G Gundam averts this with Master Asia. He can stop mecha-scaled bullets with his bare hands, kill Mobile Suits with his scarf alone, and can punch a building out of the way with his student. Size alone doesn't automatically make anything invincible here.
 * Gundam in general is all over the place with this trope. The Universal Century series have anti-Mobile Suit infantry tactics being reasonably effective while armies in the Alternate Universes generally don't field infantry against Mobile Suits at all. However one of the series' major conceits is that Mobile Suits can effortlessly take down battleships and Mobile Armors hundreds of times larger than themselves.
 * Science Ninja Team Gatchaman subverts the trope. You only needed the Gatchaman team -a Five Man Band of teenagers with a Cool Airship- to take on a Humongous Mecha and destroy it.
 * Played with in One Piece. While more powerful characters tend to be bigger, giants are easily taken down by the more powerful characters. The most brutal subversion was Oars Jr, who, though he could take cannonballs with ease and smash through smaller giants (wrap your brain around that), all it meant for the truly powerful characters was that he presented a bigger target.

Film

 * This could be the reason dinosaurs in the first two Jurassic Park movies appear to be bullet-proof. (Though granted, we puny humans rarely get a chance to even try shooting.)
 * They don't seem to be completely invincible. After all, the hunters in the second film are able to catch them in large numbers, and the movie acts as though the head hunter's elephant gun would have worked had the environmental terrorist not stolen his ammo. Also, there's the instant death coral poison gun that got tangled in some cargo netting.
 * One of the (many) common complaints against Michael Bay's second Transformers movie is the presence of human soldiers with rifles during the battle scenes. It seems that they're only there because Bay wants to see their bodies pinwheel through the air from explosions. Never mind that we see Megatron himself driven back by concentrated fire from the fleshlings.
 * In Godzilla Final Wars, fans had every reason to expect invincible kaiju. Ryuhei Kitamura attempted to overcome this trope with superhuman mutants and flying battlecruisers with lasers.
 * In Cloverfield, Word of God tells us that the traditionally unstoppable monster, but many fans and the credit sequence seem to disagree.
 * Every Godzilla movie ever. (In the original, the "Oxygen Destroyer" kills Godzilla. Still, it's not a conventional weapon, but a 'superscience' type. The SuperX in much later films has some effect.)
 * Godzilla VS Destroyah subverts this. Turns out that too much radiation can kill Godzilla. The downside is that it'll cause him to to go into a meltdown and destroy the world. Granted, nuking Godzilla is a bad idea in the first place, since it'll make him larger and more powerful before it has any fatal effects on him.
 * Subverted in GMK. Godzilla is defeated after It doesn't kill him, per se, but at least he's been
 * Averted, hard, with the film Rodan. Both monsters die in a volcano while the JSDF bombs them with an air strike.
 * Subverted in the 90s Gamera Trilogy. Gamera is easily shot down by missiles. They don't kill him, but they certainly do their fair-share of damage to the giant turtle.
 * Averted in King Kong. Kong is eventually shot down by biplanes.
 * Part of the reason for the hate for the American Godzilla movie is that this is averted. While Zilla (his Fan Nickname; the "god" was taken out of "Godzilla") is pretty much immune to small arms fire, big guns and bombs are able to hurt him, and late in the movie he is injured and eventually killed by conventional weaponry.
 * Although it isn't as bad as some would make it out to be. He survived point blank torpedoes and the first salvo of missiles before the second one brought him down.

Live Action TV

 * Ultraman lives on this. The Science Patrol always attacks the Monster of the Week with Energy Weapon handguns, airplanes, etc., but typically only Ultraman - once he's grown to the same scale as the rampaging monster - can actually defeat the monster.
 * Averted occasionally - for example, it's the Science Patrol that actually destroys Zetton (the monster who 'kills' Ultraman). It takes circumstances and (often) special one-of-a-kind weaponry, but the human teams are capable of protecting Earth on their own. It's even better when the team and the Ultra cooperate.
 * A lot of Japanese Tokusatsu shows play this fairly straight, pretty much following the examples of Godzilla and Ultraman. In fact, anytime a human-scale character offs a building-sized one, it's likely to be a CMOA of some sort.
 * In Power Rangers, if you don't have a Humongous Mecha, you should basically run. It's exceedingly rare that the most godlike weapons used at human scale can scratch the monster after Make My Monster Grow ensues. And yes, it is freaking awesome and remembered forever when a Ranger manages to avert this. (As you can imagine, of the three times it happens, once it was a Red Ranger, once it was a Sixth Ranger, and once it was Tommy.)
 * Played straight in Terra Nova. Even dinosaurs that are only slightly larger than people shrug off small arms like they're nothing. Even the mounted wave cannons on the walls of the compound only repel a ten foot tall dinosaur.

Literature

 * Averted in The Scar, where the gargantuan avanc slowly succumbs to infection after it gets injured by the grindylow. We don't actually see what weapons they'd used to damage it, but the lakeful of pus it emits while ailing is a definite sign that it's the infection, not the wounds themselves, that proves fatal.
 * Averted in Shadow's Fall, where the "unpowered" retired super hero Lester Gold takes on a T-Rex by tricking it into swallowing a grenade, leading to "your head asplode". Played straight with the Great Wurm, Cromm Cruach.
 * This is certainly the characters' initial reaction to the skyscraper-sized vordbulks in First Lord's Fury, the final book of Jim Butcher's Codex Alera, but then a few bright sparks work out their weak points...

Newspaper Comics
"Caveman: We've gotta remember that spot."
 * Parodied by one of the final unpublished strips of The Far Side, available in "Last Chapter And Worse". A man is interviewed after taking down a Godzilla-like monster with his shotgun.
 * Also averted in one depicting a massive, slain mastodon, with a miniscule arrow in its buttock.

Video Games

 * Mech Assault and The Incredible Hulk Ultimate Destruction both have harmless infantry enemies. The former is excused in that they're members a a fanatical cult who aren't afraid to die. The latter are member of the US army, but they'll try to avoid the Hulk...for the most part. If he can get close enough, they'll try rifle-butting him, which works about as well as you'd expect.
 * Mech Assault and the Mechwarrior series it spun off from actually zigzag quite a bit with this trope. Five Rounds Rapid can't do much to even a scout Mech barring extremely extended attrition but a single properly placed satchel charge can bring even a hulking Assault-class machine down and clan Elementals (or IS Battle Armor) can take down several Mechs alone if the wearer is skillful.
 * The Earth Defense Force series gleefully averts and inverts this. You play as a wimpy looking guy in a baggy jumpsuit who is tasked with killing swarms of giant bugs, towering mechs, kaiju, flying saucers, and walking fortresses. On foot. With conventional weaponry like assault rifles and shotguns. And it works!
 * The Monster Hunter series heavily averts this trope in its later monster hunts.
 * Averted by the Pokémon Wailord, who despite being the largest of all 649 of them (By a very considerable margin for almost all of them), can easily be taken down dozens of Pokemon that are anywhere from around one-tenth to one-hundredth of its size.
 * In the Dragonball Z: Budokai Tenkaichi series, Giant characters will not flinch at most smaller character's punches and almost all rush moves will ricochet off them before they can do anything. This means characters like Hercule and Videl are almost completely helpless against them.
 * Generally averted in World of Warcraft. Giants are a specific enemy type, and while they're much more likely to be elite class and therefore more difficult to defeat, they can typically be brought down just the same as anything else, and by the exact same offenses that bring down everything else.

Tabletop Games

 * Averted in GURPS. Hard. Whenever a single giant monster appears, the players tend to take it out with a single shot to the eye. Creatures that big tend to have eyes that are easy to hit, and damage multiplier tends to make even a T-Rex go down in one or two hits.
 * In Dungeons and Dragons, bigger monsters tend to be tougher, but not necessarily because they're bigger. Bigger monsters are also bigger targets.

Western Animation

 * An episode of Dexters Laboratory plays with this one: they accidentally awaken a giant Kaiju monster (it specifically happens in Japan, so it's a clear parody). The monster stomps all over a variety of superheroes and small superweapons and isn't defeated until they assemble a giant Voltron-esque robot. Though that was supposed to be an Aesop about family togetherness more than giant robots.
 * Re Boot, episode "Nullzilla" - which played off kaiju and mecha movies. The monster had to be stopped by creating a Combining Mecha.
 * In The Simpsons "Treehouse of Horror V", giant advertising mascots go on a rampage. Predictably, conventional weapons are useless, but it turns out that our attention makes them real and they'll keel over if we just don't look.
 * If it comes to that, even baby dinosaurs in The Land Before Time are harder than rocks of the same size. Although maybe it's more that those are some really sissy rocks.
 * In Monsters vs. Aliens, the army throws its entire arsenal at the giant alien robot without leaving so much as a scratch. And even after that the President shoots a few rounds at it, just to show that he's a brave President. It is then that they decide to sic the monsters at it, but even they have a hard time defeating it.
 * My Life As a Teenage Robot has Armagedroid, an older Humongous Mecha designed by Dr. Wakeman, which fits this trope to a T. There are a couple of other giant-sized threats throughout the show, but Jenny is able to beat them with some sort of force.
 * Despite the aversion in the American Godzilla film, Godzilla the Series plays this straight. Godzilla in this series, is now capable of taking multiple hits from weaponary from humans AND aliens. Not only him, but the other monsters that appeared in the series. The only time they would die is by Godzilla or the Leviathan alien's weapons. And fighting each other.

Web Original

 * EVERY. MACROPHILE. STORY. EVER. Every one there has ever been or ever will be uses this Trope extensively, and even taking it to ridiculous extremes.
 * Some stories, artwork, and etc do try and be more intelligent about it. Though as often as they run afoul of the Square Cube Law, most handwaves for that issue tend to get applied to this trope as well.

Real Life

 * Perhaps not as ridiculous a trope as it seems; a 50 meter tall, 20,000+ ton monster would most certainly need to be made of a very strong and durable substance, simply to keep itself from falling apart at the seams. Any monster that huge that was so flimsy as to be vulnerable to conventional weapons would be squashed by its own mass before we'd ever need to fire a shot. If on the odd chance you ever do meet a kaiju IRL and it doesn't collapse into jelly the moment it steps out of the ocean, you can safely assume this trope is in effect.
 * Considering a simple hunting rifle can bring down an elephant, this is definitely not Truth in Television, even in the rare cases there are big things to shoot at.
 * With a much more relative definition of "giant", this applies to all macroscopic life. Nearly anything can be taken down by an infection by much smaller organisms (such as bacteria or viruses).
 * They are resistant to many small arms fire, that is what elephant guns are for.
 * Elephant guns aren't strictly necessary for elephant hunting. In the olden days of unregulated slaughter for ivory many an elephant was killed with the lowly 7x57mm hunting cartridge, today now mostly used (at least in the United States) to bring down the relatively tiny whitetail deer. The main advantage of said "elephant guns" was that they could bring down very large game more quickly and more reliably. You could kill an elephant with a 9mm pistol if you had to, but it'd take a while (not as in shooting it until it dies video game style, but rather in waiting for it to bleed out, or with less severe injuries, wait for an infection to develop, since a small cartridge would have a hard time piercing the skull or penetrating to an internal organ). A more powerful firearm has the advantage of being able to bring forth a quicker death from farther away (which helps considering that said elephant may be trying to kill you), but once it dies, dead is dead one way or another.
 * Whales can be killed with a simple harpoon, but its not as easy as it seems as they need to nail it at the right spot to make it effective. Then came grenade harpoons.
 * Real Life massive vehicles of both civilian and military types are largely immune to or not significantly compromised by most small-arms fire, which is the reason that specialized anti-vehicle and anti-materiel weapons (which often have firepower on the same scale as the vehicles themselves) exist. Giant aircraft are slightly more susceptible due to the mechanical balancing act that keeps them aloft but a platoon of infantry would still need a lot of lucky assault rifle shots to down a heavy bomber if it somehow came within range.