Undefeatable Little Village

All of Gaul is conquered? No. One small village still held out against the Roman invaders!

It is such a friendly, peaceful little place.

In spite of being surrounded by the big malevolent empire, and technically being at war with it, the village is not the least bit warlike or aggressive. Yet the empire keeps sending its great legions, and the little village keeps crushing them all as if they was simply swatting flies. Perhaps it is a Town with a Dark Secret, or populated by Badass Crews, or maybe a Knight Errant visited in the past and took to Training the Peaceful Villagers. Whatever the reason, it's practically invincible.

While the "village" can be some other form of small civilian community (a block in a city, for example), it must still be small and civilian. Military outposts do NOT count, and neither do entire cities or full sized countries. So, no, 300 is not an example.

While the "Empire" can be some other form of huge monolithic force (a megacorporation or international crime syndicate, for example), it must still be huge, powerful, prone to violence, and known for conquering all in its way. A single country, normal corporation or criminal gang will not do.

Compare Hidden Elf Village, which stay independent through not getting detected instead of crushing all the hordes the empire sends against it. Also compare David Versus Goliath. Frequently caused by a Superweapon Surprise.

Examples of Undefeatable Little Village include:

Comic Books

Asterix is probably the Ur Example.
In the Fables album "The Good Prince", The Empire is severely shaken by such a village, having sent more troops against it than it could afford to lose.

Film

In Kung Fu Hustle, Pig Sty Alley is this kind of village within a larger city dominated by criminal gangs.
In Ip Man, master Yip trains his entire local village in wing chun to fight off bandits.
In Star Wars, the Ewoks are a sort of midget Teddy Bear take on this.

Video Games

Although Asterix comics are one of the best-known examples of this trope, the video game adaptation for PlayStation strays away from this by having the player take back the Gaulish territories.
In Heroes of Might and Magic III, the town of Fair Feather fills this role in the campaign mission "Guardian Angels". As the name implies, the reason for the town's survival is because Angels are guarding the town, which the player can recruit and promptly turn the whole mission into a cakewalk.
In Fallout: New Vegas, Goodsprings is one of these, if you decide to help them drive away the Powder Gangers.
- The Boomers are another example—except for the fact they have howitzers, missile launchers, assault rifles and eventually a WWII bomber on hand.
- In Fallout 3, you can train Big Town to be one.
At the beginning of Shadow Hearts Covenant, the village of Donremy, France fits this, because Yuri is there. Once Yuri is cursed and has to leave, it falls to the German advance.
In Arcuz, the titular village appears to be this, given the lack of other (visible) towns. The intro sequence seemingly hints that they were all destroyed.

Literature

For a time, Emond's Field in The Wheel of Time became this trope, fighting off way more Trollocs than it had any right to using little more than skilled archers and a sheer stubborn refusal to lose.
Pretty much the entire premise of the Redwall series.
A science fiction story posits a scientist living on an island creating a population of small, intelligent creatures that live short lives in an ammonia environment in tanks in his lab. He communicates with them through a teletype connection (it's an old story). They make many great inventions for him because their generations are short in time, so many generations can work on a problem. The outside world wants them, so the navy is poised to attack him. He requires his creatures to build a completely impregnable shield around the island, which they do. The navy spends the rest of time bombarding the grey sphere, and he spends the rest of his days with his creatures. I forget the name of the story and the author. Can someone supply them please?
- "Microcosmic God" by Theodore Sturgeon, perhaps? This troper asked for an ID of one collection that it appeared in, on Usenet, some years ago.
The Santaroga Barrier by Frank Herbert. A small, somewhat prosperous farming, cheese-making community... with but a few insignificant anomalies. Except no one who isn't a local can get any foothold, not even big corporations. And people who start looking too aggressively into what really isn't their business tend to end up in a fatal accident due to freakish coincidence of several apparently innocent random events and minor mistakes.

Web Comics

During an arc of Sluggy Freelance, it's revealed that a small town near the Canadian border ended up playing this role for a crime-syndicate who had, previously, used it as a center for their smuggling operations. The reason? Knife Nut Tyke Bomb Quasi-Immortal Oasis, whose most recent reincarnation had turned out unusually sane and kindhearted, had made it her Protectorate. Wearing a red hoodie, she turned into the vigilante 'Red Riding Hood' and basically stabbed any criminal who dared enter the city. The syndicate finally sent a top-tier, highly-paid Career Killer - a master assassin. He managed to kill her, but obviously didn't know about the 'Quasi-Immortal' bit, and wound up getting stabbed anyway. He sought alternate employment with great rapidity at that point.
In Looking for Group, A Little Village Up the Coast appears to fit this trope until the arrival of missionaries and soldiers from the empire, at which point it's revealed to be populated by an undead Badass Crew and houses the Amplifier Artifact of an all-powerful warlock.

Web Original

The village of Felton tries to be this in the AlternateHistory.com timeline Protect and Survive: A Timeline. It fails. Choose the fucking cowboys. Especially when they've got a fucking tank.
Felarya has Safe Harbor, which has weathered a series of attacks by man-eating predators, hostile humans, and other ills. It owes its continued survival to Jade, a badass giantess who absolutely destroys anything that threatens it.

Real Life

Pavlov's house during the battle of Stalingrad.
Brazil's Canudos village definitively applies, even if it went down in the end.