Boisterous Weakling

Some characters like to brawl, mock authority and protocol, and will fight eagerly.

This character is just as loud and doesn't like to be ordered around. But contrary to the Boisterous Bruiser… he doesn't really have much to back it up. He is physically (and maybe emotionally) weak but that doesn't stop him from constantly calling out those who glower at him (or so he thinks). Sure he may pick on people weaker than him, but if he happens to realize his opponent can effectively kick his ass, either he will find a lame excuse, or insist and get his ass kicked. Or both. Don't expect that to make him think twice the next time, though: the Boisterous Weakling shows an astounding inability to acknowledge his own impotence. Even if he tries to bite, he has no fangs.

Often Played for Laughs. If the author likes the character enough, he may pull out a Not So Harmless Villain/Let's Get Dangerous moment or even Take A Level In Badass.

Can overlap with Fearless Fool, Miles Gloriosus,Small Name Big Ego or Super Loser. Compare Fake Ultimate Hero and Feet of Clay, when the character is alleged to be strong by other people. Contrast Gentle Giant. Also contrast the Smug Super, who will usually have very good reasons to be smug.

An intellectual equivalent would be Know Nothing Know It All.

Anime & Manga

 * Vinland Saga has Ormar, a rebellious punk who only dreams of the battlefield, gets into arguments for nothing, and is always talking about the "honor of Nordic warriors". But whenever he has to actually use a sword, it's painfully obvious he has no skills whatsoever. When we first see him, he can't even draw his sword properly.
 * He becomes less boisterous
 * Haruka in the Mai-HiME anime, despite being a totally normal, powerless human and totally overwhelmed by the situation, will not let you forget that she is in command. She doesn't hesitate to face tanks and soldiers and even provoke a HiME In her case, these guts are actually what makes a good part of the fandom like her.
 * Mr. Satan in Dragonball is actually rather strong for a normal human, but inevitably fails to notice that the monsters he taunts and challenges can disintegrate him effortlessly or destroy planets on a whim. He gets better near the end of the series, though.
 * Black☆Star is essentially this at the beginning of Soul Eater, constantly boasting about his strength and announcing his strategies out loud, which then leads to his ass getting kicked.
 * The Team Rocket in Pokémon is a trio of this, although Jessie and James use their Pokemon instead of doing the actual fighting themselves.
 * The titular character of Naruto was this as a child and at the very beginning of the series. As soon as he learns the Shadow Clone Technique though, he takes levels in badass for breakfast.
 * In Daily Lives of High School Boys, Sanada North's Student Council President starts a fight against Sanada East's counterpart Ringo only to get his ass kicked without landing a single punch.

Comic Books
"The Punisher: Most wiseguys are one part street-smarts to two parts muscle. Enough to terrify the mooks that owe them money, but not much more."
 * Marvel Comics' Volstagg is somewhere between this trope and Miles Gloriosus Depending On the Writer.
 * Many minor Batman villains of the early Silver Age turned into this in The Dark Age of Comic Books, since they remained active supervillains but had their skills downplayed and their ridiculous motifs played up. Typically, they'd show up, full of bluster, and be dropped within a page or even a panel. Killer Moth, Catman (before writer Gail Simone rescued him), and the 1940s version of the Cavalier all got such treatment at various points.
 * Many criminals in Judge Dredd talk tough...but they can never stand up to a Mega-City Judge.
 * In The Golden Age of Comic Books, this was the role of many a teen sidekick.
 * The vast majority of the criminals seen in Garth Ennis's Punisher comics are tough-talking, gun-happy street criminals...but when they go up against Frank Castle, a trained soldier with military equipment, they're far less powerful and dangerous than they imagine. It's even Lampshaded in the first issue of the MAX series.

Films

 * 'Ol' Cigaret' in Emperor of the North is always boasting about how he's the toughest hobo riding the rails, but the real veteran 'A-No. 1' has his number right from the start. At the end of the movie, he's so fed up with Cigaret's bragging that he just picks him up and throws him off the train into a lake.
 * Ike Clanton in Tombstone is a loudmouth who starts several gunfights, but he's always the first to fall or flee despite his bravado. The obnoxious, bullying casino employee at the beginning, played by Billy-Bob Thornton, is another example.
 * When "Happy" Hogan and the Black Widow infiltrate Ivan Vanko's hideout in Iron Man 2, Happy comes off as this in comparison to the more skilled Natasha.
 * Ash Williams plays this part throughout much of Evil Dead 2 and some of Army of Darkness, but by the end of each film, he's become the catchphrase-tossing, boomstick-toting badass we all know and love.
 * Jack Burton in Big Trouble in Little China, thanks to a healthy dose of Wrong Genre Savvy.

Live Action TV

 * For a while in Buffy the Vampire Slayer, this was Xander's role, thanks largely to his becoming Overshadowed By Awesome but still insisting on joining in the battles.
 * An even better Buffy example might be Wesley Wyndham-Pryce, at least before he Took a Level In Badass in the Spin Off Angel. Even there, it took some time for him to become as formidable as he initially thought he was.
 * In Lie to Me, Cal Lightman is thwarted at any bit of assault toward him. He is occasionally battered.

Real Life

 * There is a joke about a small animal (told in Russia about a hedgehog) standing and shouting "I am strong! I am strong". A passing bear gives it a kick. The hedgehog flies a few meters, stands up, brushes itself off and shouts "I am light, but strong!"
 * In professional wrestling, this is thrown around a lot with heel characters. While how pathetic they actually are varies, almost all heels are cowards to some extent and tend to suffer some mild Badass Decay when they make a Face Heel Turn. A very common running concept is for a heel to mouth off and boast at a face about how he is going to kick the latter's ass, only to be quickly knocked down or sent running when the face decides they've heard enough. Chris Jericho and The Miz are key modern examples (even if they prove to be more than all talk on occasion).
 * Small dogs fit this troop.
 * Vets call it BDLDLDL: Big Dog, Little Dog, Little Dog Lost.

Theater

 * Sir Andrew Aguecheek from Shakespeare's Twelfth Night. According to Maria, he loves arguing so much that the only thing saving him from an early grave is the fact that he's a coward. Sir Toby gets a kick out of urging him to write a highly insulting challenge for a duel, then feeding him false information to the effect that his opponent is a skilled and ruthless swordsman. (In reality, his opponent is the local Sweet Polly Oliver, and Toby is intentionally setting up a Wimp Fight for his own amusement.)

Video Games

 * Dan Hibiki from Street Fighter likes to boast about how strong he is and invites people to learn martial arts from him, but he's actually hilariously incompetent.
 * Sir Prancelott of Scufflewick in Drakensang always talks about his wondrous deeds.... except that he's the greatest Ted Baxter of Aventuria, his sword skills are useless, he can barely hold his own against a wolf and runs away from some goblins (later claiming that he was taking their attention away from you) and the only time he tries to take on a Linnworm (huge multi-legged reptile), he's knocked unconscious by the beast's breath.
 * Von Kaiser in both of his appearances in the Punch Out series.
 * In Mother 3, the Mole Crickets are an entire species of this, at least until their champion is defeated with ease by the protagonist.
 * Nanoe Kanetsugu the INVINCIBLE from Sengoku Basara. He's the games' official Chew Toy Joke Character who is about as endurable as your average Mook, but that doesn't stop his boasting.

Web Original

 * In Doctor Horribles Sing Along Blog, Captain Hammer is perfectly happy to beat up nonpowered folks, he's not actually that talented a fighter, continually lets his enemies escape, and once he's actually injured he becomes a blubbering mess.

Western Animation

 * One of the reasons Scrappy-Doo is the trope namer for The Scrappy is his habit of picking a fight with vilains obviously stronger than him.
 * Eric Cartman talks a big game, but when it comes to actual combat, he usually can't follow through. In one notable example, one mild slap from Kyle sends him crying to his mom.
 * Daffy Duck, despite being a self proclaimed "craven little coward", has a tendency for flapping his big beak about his bravado and smarts and trying to place himself in the role of The Ace, usually literally getting in the face of someone way out of his league.