Larfleeze, the wielder of the orange light in the Green Lantern universe. Most of the time, he comes off as completely insane, with a Gollum-like drive to own everything and a tendency to talk to himself. At one point, Sinestro and Atrocitus get so annoyed by him they suggest just killing him and taking along whoever his ring goes to next. Despite his Cloudcuckoolander tendencies, however, he's incredibly powerful, as his light represents avarice, and is at its most potent when wielded by one lone ringslinger. In terms of sheer raw power, he's probably the strongest Lantern as his ring is capable of charging to 100,000 percent energy- in comparison, Hal Jordan's maxes out around 210% under certain circumstances, and it's explained any more might blow up the ring and take his hand with it. Insane? Yes. Take him lightly, though, and you're dead.
All those Orange Lantern constructs he has hanging around? He killed them and took their identities to serve him.
Squirrel Girl, hands down. Cute. Fuzzy. Talks to squirrels. Lips taste like hazelnuts. Defeated Doctor Doomnote which, before you ask, was not retconned as being Actually a Doombot, The Mandarin, Giganto, M.O.D.O.K., Thanos, Terrax, Bug-Eyed Voice, Bi-Beast, Deadpool, Pluto, Fin Fang Foom, Baron Mordo, Korvac, and Ego the Living Planet...
Somewhat related is The Fabulous Frog-Man. Fat, clumsy, untrained, and with no idea what he's doing, he's proven time and again capable of taking on the most nefarious villains and coming out on top. Usually by virtue of sheer luck or coincidence, but he often exhibits the bravery necessary to charge at baddies who give Captain America pause nonetheless.
Plastic Man has been largely considered this due to the non-serious nature of most of his appearances. One must not forget that he is a trained CIA operative, can go toe-to-toe with many other big names in the DCAU (he can take punches from SUPERMAN without so much as batting an eye!) and survived dismemberment for thousands of years.
Scott Pilgrim. Face it, you too though he was just a 23 year old hipster video gamer slacker without any shame or glory, hanging onto his gay roommate to pay for everything, and just being a bad bass player on a semi crappy band. Then, the first evil ex of Ramona came, and we learned that not only is he capable of fighting, he's the best fighter in the province. Dumb and with a little of OCD, yeah, but don't mess with his girlfriend or his friends.
Monchito from Negation. Most of the time he does little more than eat a lot and get underfoot, but in a highly stressful fight scene late in the series, he hulks out and gets uber-powerful for a brief moment, clobbering one of the bad guys and expending all his power in one blow before reverting to normal. Even the bad guys were shocked.
Deadpool sometimes slips into this, Depending on the Writer. His Cloudcuckoolander tendencies and ability to both shake off bodily harm and make a joke of it tend to obscure the fact that he is an immortal, unstoppable, superhuman killing-machine with a penchant for inventively torturing and/or brutally slaughtering anyone who manages to get on his bad side.
In the "Deadpool Kills the Marvel Universe" miniseries, he single handedly slaughtered nearly every superhero on the planet. This was caused when Psycho Man fiddled with Deadpool's brain until something clicked, turning him into the perfect killing machine with a penchant for nihilism. He resolved to destroy reality itself, believing that it never mattered anyway, due to him being aware that he is a comic book character. This is proof that he isn't just being capable of fighting A-list Marvel heroes and villains, he is capable of murdering every single one with ease.
Kasumi of all people managed to MacGyver a fuel-air bomb using the Dojo's oven, flour, spices, and a bottle of cooking spray to knock back a trio of Youma in War in Tokyo. She comments that she used too much Cayenne in a complete normal tone of voice. Genma and Soun only stare at her.
Also the above is very possible. Old Mills have a tendency to explode when too much dust is in the air and something sparks it. Though it's really hard to get the fuel-air ratio right, especially while your father and his friend are fending off a dozen Youma.
Burning Black: Cosmo. The changes are so abrupt at times, it's frightening to anyone who witnesses it. It's especially alarming to Wanda and Anti-Cosmo, as the change comes with hyper-competence and he's not supposed to ever get smart.
In a number of He-Man fanfictions, Orko gets quite upset when someone hurts Teela.
Shikamaru in Kitsune no Ken: Fist of the Fox. Of course, we already know from the canon Naruto series that he's this, but in this fic, he is so lazy that he prefers watching clouds to buying his own lunch at school, yet he was able to point out flaws in Tenten's defense even while groping her naughty bits during their fight in Sasuke's tournament, and later on he knocked Aoi unconscious with one punch during said tournament.
The Incredibles: Jack-Jack (not a moron, but a baby) demonstrates a startling array of powers (which, by most reckonings, are probably more Bad Ass than those of the rest of the cast) when threatened by the Big Bad, Syndrome.
Or the babysitter. In the fairly amusing short packaged with the DVD, Jack Jack Attack, Jack-Jack reduces the babysitter to a stress-overloaded wreck by spontaneously generating anti-gravity powers, teleportation, the ability to shoot Eye Beams, and Human-Torch-esque flame powers. Since the whole film seems to be a Homage to the Fantastic Four, he might be a sly reference to the fifth Fantastic: Franklin. The writers, for their part, note that the reason they gave him so many powers he flips through like he's channel surfing is because he's a baby: he hasn't defined himself yet. What this means for the world of The Incredibles as far as power development goes...
The babysitter herself qualifies for this trope. She starts out just seeming to be a typical teenage ditz. She not only gets though the short alive, but able to counter most of the effects of Jack-Jack's powers (albeit with some minor property damage).
The CGI movie The Magic Roundabout, in which the affable stoner rabbit, Dylan, suddenly snaps and opens up a can of Whup Ass.
An American Tail 2: The only nice cat, who gets repeatedly pushed around, abused, and chased (either by dogs, native american mice, or even dog fish!) all the way to the American west, takes a level in badass when he gets trained by a reluctant aged, canine gunslinger. When he sees his love in danger, he goes into a literal barking rage and takes down almost the entire Big Bad's cat mook army.
Po from Kung Fu Panda. While not totally inept, he's a bumbler and a daydreamer. After some focus and hardcore training, however, he not only managed to take down the Big Bad, but his idols are so impressed, they kneel before him.
Cars 2: Mater, oh excuse me Sir Tow Mater. He spends most of the movie being his lovable bumbling self. Then he finds out Lightning McQueen is in trouble. Lesson when dealing with Mater, NEVERthreaten his friends, just ask the three or four bad guys he took BY HIMSELF.
Captain McCrea of WALL•E goes from the typical clueless, near-helpless human aboard the Axiom to the first human to stand under his own power in centuries, deactivating the mutinous taser-wielding Autopilot.
Scuttle from The Little Mermaid. He has a total misunderstanding of things from the surface world and is the comic relief for most of the film, but he organizes an entire army from above and below the waves to stop Ursula from marrying Eric.
"We gotta find a way to stop that wedding!"
Captain Haddock in The Adventures of Tintin is a perfect example. He's a complete idiot, but his brute strength comes in handy. In a simultaneous Crowning Moment Of Awesome and Crowning Moment of Funny he crawled out of the cockpit of a seaplane that was running out of gas while it was flying in midair and breathed into an exhaust pipe so that his alcoholic breath could fuel the plane on its fumes for a little while longer (even if it didn't exactly work as planned).
At the end of One Good Turn, Stan snaps and starts physically attacking Ollie while shouting threats. The boys added this in because Stan's little girl was scared of her "Uncle Ollie" (she thought the way he bullied Stan in the films was real); seeing a movie where her dad finally stood up to him completely fixed the problem.
This was also an example of Serendipity Writes the Plot: The ending was improvised because Stanley's daughter was actually on the set that day and he wanted her to be happy.
In Block-Heads, the boys have a run-in with a bratty little kid (played by Tommy Bond, aka "Butch" in The Little Rascals). This leads to the kid's father twice kicking Ollie in the rear...for which Stan retaliates in turn by landing a punch on the guy's chin that knocks him out cold.
In Two Tars, they push a man hard enough to send him flying into his car-which then falls over.
The Quick and the Dead: Cort starts out this way, a somewhat awkward, hapless preacher who initially seems to be way in over his head when he's forcibly entered into the quick draw competition. He refuses to participate and repeats over and over again that he won't draw...until the clock strikes the hour and he's shot his opponent without even seeming to realise it.
Sing, the hapless hero, starts off as a complete failure of a small-time street crook. Then he double-crosses the Axe Gang, gets beaten into a bloody pile of meat — and wakes up as an indestructible kung fu god.
Just about the entire cast fits this trope. Ranging from the pervy landlord and bitchy landlady, to a secretary geek wearing golden glasses kicking both Sing and his partner's arse, and the farmer lady who managed to make Sing vomit blood with a punch — there are loads more.
And then there's The Beast. He's built up like some kind of monster when Sing is sent to recruit him, and when the audience finally sees him...he looks like a balding homeless man in a wifebeater, boxers and flip-flops, and acts very silly and nonchalant. The Axe Gang are torn between taking him seriously and thinking they've been had...until he kicks everyone's ass and usurps the position of Big Bad.
Police Academy 5: Assignment Miami Beach had Commendant Lassard being kidnapped and held hostage by the Big Bad. He mistakenly thinks it's all a game being put on for the media, and when someone points out that it's not, he rather quickly frees himself without breaking a sweat.
Get Smart: Maxwell Smart is ridiculously skilled and resourceful, an excellent marksman, and really damn lucky. Except for when it's funny for him to be an idiot.
Loren Visser, the private detective in Blood Simple, comes across as a goofy, loudmouthed, dumbass joke at the start of the movie...until he shoots Julian, the man who hired him. From then on, he's a nigh-unstoppable killer.
In Galaxy Quest, Sir Alexander Dane spends most of his time complaining, about the degeneration of his career from classically trained Shakespearean actor to being most famous for his role as the token alien in a cheesy space opera. But when an alien trooper shoots his biggest fan, the character dies in his arms while saying that he always thought of Dane's character as a father figure. Dane then utters the alien vow his character is known for, which he had utterly hated up to this point, swearing vengeance, and lunges out of cover. The alien trooper takes aim at him but he charges, bare-handed. The alien's gun fails just in time for Dane to leap on top of him and start beating him to death bare-handed—which in turn gives the rest of the Thermians the courage to join in the fight.
Elle Woods from Legally Blonde. She starts out appearing to be The Ditz, but apparently superior knowledge of fashion and haircare do not preclude intelligence.
Dodgeball: A True Underdog Story has Gordon Pibb, a bumbling loser whose mail order wife hates him and who can't get angry or throw a ball with any force to save his life, making him the weakest link on the Average Joes team. However, that changes during the semi-finals. By himself against almost the entire opposing team, he sees his wife having fun with another guy and gets super pissed, going psycho and single handedly taking out the entire opposing team.
The scene in question may be a homage to the original Rollerball. The film climaxes its over the top sermon on individuality vs. collective thinking and sports fixing by having the hero's team deliberately killed off all around him, until the quiet rebel in said hero snaps and he brutally destroys the entire opposing team by himself before scoring a goal nice and slow to drive the point home.
Kwan-Yin from the Journey to the West TV film kicked demon ass without breaking her Goddess hand gesture.
Mystery Men's Mr. Furious, when his love interest was threatened, wiped the floor with Casanova Frankenstein.
In the 1986 film Aliens Private Hudson (Bill Paxton) would like to be viewed as a badass but is constantly slapped down by his more-badass companions and spends much of the film whining and complaining — until the chips are down, when he goes into full badass mode and mows down countless aliens before falling.
"Come on you bastard! Come on, you too! Oh, you want some of this? Fuck you! FUCK YOU!"
Wikus van de Merwe of District 9 is a sniveling, naive corporate pencil-pusher with a silly mustache - and when the chips are down, he climbs into a suit of alien Powered Armor and proceeds to vaporize the local voodoo gang as well as the psycho PMC troops sent to retrieve him.
Zen from the Thai film Chocolate is a severe autistic, yet has the ability to watch a martial-arts fight and absorb the various movements. In a point of awesome, the martial-artist playing Zen really does learn at least a dozen separate fighting styles for the movie, and displays them flawlessly.
The Toxic Avenger: Melvin worked at the Tromaville gym, Ninety pound weakling who got pushed around!
Unleashed stars Jet Li as the slave-enforcer of a British gang boss, raised as something approximate to an attack-dog, leaving him with the mind of a child. In fact, the character only achieves contentment when he is able to abandon his history of violence and embrace a life of non-badassery.
Tuco, "The Ugly" from The Good, the Bad and the Ugly, is a hairy, goofy, slovenly klutz compared to the more mature, soft-spoken and reserved Man With No Name and Angel Eyes (not unlike Daffy Duck, actually), but is capable of shooting with incredible speed and accuracy, escaping from an armed guard by cunning use of the train tracks, as well as nearly killing Blondie several times only for him to be saved by luck (or cannonfire).
Star Trek. Yes, James T. Kirk is a brat, a chronic juvenile offender, a wanna-be ladies man, and he seems to excel only at getting beat up. He is also the baddest mother in all of Starfleet, and not even killing his dad or blowing up planets will change that. You may now go to warp.
Well, considering that Vulcans and Romulans have three times the strength of an ordinary Human, you have to give him props for still attempting to take them on. He does slightly better in the barfight with the human cadets, having only lost because he was clearly outnumbered.
Count Vile from Press Start spends most of the movie acting like a complete dolt, leading many to question how he managed to assume total control, only revealing his true power and psychopathic ferocity in the final battle.
Perpetually horny CIA operative Colette Dubois (Anna Nicole Smith) in the unbelievably cheesy erotic thriller To The Limit is a bit of a question mark. Most of the time, she seems to almost have the mind of a child and doesn't even try to come off as anything but The Ditz. When it's time for action, however, she can inexplicably hold her own in fights with ninja assassins and coolly kill whole carloads of villains. It's all very bizarre even by the standards of a bizarre movie, and leaves one wondering whether Colette is actually this or another practitioner of Obfuscating Stupidity. But considering Anna Nicole's real-life persona...
Evil Dead: Ash is for the most part a total idiot; but if there's one thing he's good at it's making dead things deader.
Star Wars: Jar Jar Binks (who else?) - Anyone else remember how essentially all of the droid kills he managed to get during the Battle of Naboo were entirely by accident and a result of his incompetent screwing around? As long as he is free to be a complete klutz, that guy is a walking, er, stumbling disaster zone.
The Gungan commander tries to toss him a booma (plasma grenade ball), which he juggles around for a second or two before dropping it onto a droid driving a tank (of which Binks is straddling the cannon), causing said tank to crash.
When he's on the ground, he gets his foot caught in some exposed wiring from a droid that's been torn in half (but still semi-operational), and his attempts to shake it free cause the droid to fire its weapon at other droids, scoring some kills.
When the Gungan forces retreat, Binks tries to grab the tailgate of an ammunition wagon in a desperate attempt to avoid being left behind, but instead causes the tailgate to fall open, spilling the plasma balls down the hill and onto the advancing droid armies.
Also from The Phantom Menace, Ben Quadinaros is introduced as an inept Podracer who previously raced on only the safest tracks and mocked by the other pilots for trying to take on the dangerous Boonta Classic. Not helping his reputation is that his Podracer malfunctions and falls apart before he can even pass the starting line. He seemed to have manned up following the Boonta Classic, however, as he has since become highly skilled at navigating the Inferno, a course considered difficult and extremely deadly even by Podracing standards, and after that, winning races on locations taken seriously by high-level Podracers that he achieves status comparable to celebrity champion Sebulba. He is still incredibly meek and timid off the racetracks though.
Yoda seems this way at first in The Empire Strikes Back, but is largely considered the philosophical heart of the franchise.
Abby in Death Proof. She disapproves of Kim's gun and whines a bit. Until the Big Bad attacks them that is. She's the one who suggested killing him and later stomps in his head after beating him up
Subverted in Indiana Jones and the Last Crusade. Indy has given his father's Grail Diary to Marcus Brody, an apparently goofy, harmless professor. The villains indicate that Brody will be easy to find, but Indy tells them that Brody fits this trope.
Walter Donovan: He sticks out like a sore thumb. We'll find him. Indiana Jones: The hell you will. He's got a two day head start on you, which is more than he needs. Brody's got friends in every town and village from here to the Sudan, he speaks a dozen languages, knows every local custom, he'll blend in, disappear, you'll never see him again. With any luck, he's got the grail already.
The camera then cuts to a scene of Brody in a crowded market, conspicuously wearing the same thing he always does, calling out "Does anybody speak English?" He eventually redeems himself by clonking a Nazi unconscious with a bottle while in the tank.
Played straight with Indy's father Henry. Throughout much of the movie, he comes off as comically aloof, but he takes down a Nazi fighter plane by scaring some seagulls with his umbrella.
Henry: I suddenly remembered my Charlemagne: "Let my armies be the rocks and the trees, and the birds in the sky!"
Mamiya in Cure: seemingly unaware of his identity or surroundings, but a master of hypnotic suggestion who is capable of taking command of another person's will in a matter of seconds. He's accused of Obfuscating Stupidity, although this is never made explicit. The fact that the detective's wife definitely suffers from such an ailment adds to the uncertainty.
Both Scooby Doo AND Shaggy step it up at the end of Scooby Doo Monsters Unleashed, although they tried (and failed) throughout most of the movie.
At the start of Lawrence of Arabia, T.E. Lawrence is stationed at a humdrum position in Cairo, and most of his fellow officers view him as insurbordinate and quite the eccentric. It's only after he's sent on a mission to Arabia that he reveals himself to be a superb military commander.
Danny Kaye's character Hawkins in The Court Jester is The Fool. Literally, since Hawkins is playing the character of Giacomo, "King of Jesters and Jester of Kings," in-universe (it's that kind of movie). Then he gets hypnotized into believing he's essentially Don Juan and Musashi all rolled into one. Pity that the switch between Hawkins (who barely knows how to hold a sword) and his hypnotized alter ego is the sound of a finger snap. Cue the most epically hilarious swordfight ever filmed.
Hawkins: And now, Ravenhurst, your life isn't worth that *snap*! Ooooh...
The Sandford PD from Hot Fuzz. For all their weird ways of doing things, and their almost naive, Cloudcuckoolander personalities, they excel at armed response.
Radagast from the film adaptation of The Hobbit. Though eccentric (he lets birds nest in his hair, and Saruman is convinced that eating so many mushrooms has affected his brain), he is able to bring recently deceased animals to life, outrun wargs on his sled, and even defeat the Witch King in hand-to-hand combat without breaking a sweat!
Natalie Voss, the rich girl in The Chase. Kidnapped at a convenience store, she begs for her life, vomits in terror, and shrieks so loudly and shrilly that her suave, dark-haired kidnapper (who else but Charlie Sheen?) can just barely tolerate her. As the getaway car heads to Mexico and Natalie gets to know her captor a lot more, learning that he's actually an unjustly accused criminal acting out of desperation, she not only grows to like him but realizes that he's her ticket out of her stiflingly buttoned-down existence. When Sheen's character is finally caught just short of the border, Natalie sees him getting hauled into a police car in handcuffs and, realizing this is her last chance to escape her former life, and despite never having handled a gun before and in fact finding guns repellent, steals a gun from one of the police officers, puts him in a headlock...and after her father scolds her for pretending to defy him, shoots a nearby hovering helicopter right out of the sky with one shot from the pistol. This sudden feat takes everyone aback - not least of all Natalie herself, who for a moment can do nothing but stare saucer-eyed at her handiwork as if to say, "Did I do that?"
In general, many Lets Players and internet personas in general are this. Just because someone likes to goof off and make bad jokes doesn't mean they're not intelligent and competent.
Simon Lane and Lewis Brindley of the Yogscast usually play quirky Idiot Heroes. And then you hurt someone they like, and they will kick your ass. Not to mention that despite their usual stupidity they both have studied advanced sciences in real life.
Sips is one of the go-to goofballs, frequently spelling things wrong and neglecting his grammar, while making bad jokes. He's also one hell of a gamer when he decides to stop messing around.
Hat Films enjoy frequently verbally abusing one another, constantly end up hurting or killing themselves by accident and often impede their own progress, but they've designed very efficient mob grinders and ways to retrieve underwater gear, won many PvP maps and regularly manage to give Sips and co a good run for their money.
Achievement Hunter, with the exception of Ray Narvaez Jr. and Ryan (whose in-series persona is very crazy), are all rather quirky and have regular moments of stupidity. In spite of this, every single one has pulled off some crazily impressive stunts, being good gamers when push comes to shove. Of special mention is Gavin Free, who for the most part speaks in a somewhat unusual manner and serves as The Load.
Inverted with Japanese singer Gackt. He often portrays himself on TV as a stoicbadass with few emotions and exceptional martial arts skills...until he answers a silly or private question, thus revealing himself as a hidden dork with a habit of saying goofy or embarrassing things.
This is especially evident in Gackt's later "Platinum Box" DVDs. No matter how hard he tries to remain serious and stoic, his bandmates will always reduce him to hysterics with their shenanigans, shattering his well-practiced persona.
In an early Bloom County strip, Opus serves as the bouncer at a New Years Eve party. Seems pretty stupid, until he drags a particularly large, menacing looking guy down under the bar, then asks for some rope.
And if you are a mime, do not taunt Opus or he will beat you down. With a salami!
Wasn't it an olive loaf?
Typically, the Crocodiles in Pearls Before Swine are Too Dumb to Live (oftentimes literally so). But on one occasion, Rat, in a variation of the Pied Piper, used music to lead stupid people to a lake to drown them. When he attempted to do this to the Crocs, he gloated about this, and in an uncharacteristically angry (but characteristically badly-pronounced) reply, one croc mentioned "We can sweem."
This could be Canon Discontinuity (which Stephan Pastis is infamous for), because an earlier strip had one of the crocs drown in a kiddie pool because he couldn't swim.
Satchel from Get Fuzzy. The guy has about half the IQ of a rock, but as Bucky is often reminded, pushing Satchel too far is a very bad idea.
WWE worker Festus has this as his entire gimmick. Most of the time, he was little short of catatonic, staring blankly into space with his tongue hanging out as his tag team partner Jesse dragged him around. However, when the ring bell rang, he would wake up and destroy all of his opponents, and would not let up until the bell sounded the end of the match.
Unfortunately for Festus, several of his opponents (notably The Miz and John Morrison) have shown themselves to be fairly Genre Savvy in using this against him.
Pick any sportsperson who occasionally excels in a discipline within their sport that they aren't expected to.
Australian cricketer Jason Gillespie once famously scored 201 not out after being temporarily promoted in the batting order as a "nightwatchman" - the only batsman with an average under 20 ever to achieve this milestone. The very important qualifier is that this was against the highly unskilled Bangladesh, but that doesn't explain how he was able to outperform the other five batsman who batted before Australia's declaration, all of whom had averages roughly two and a half times that of Gillespie. To top it off, Gillespie took 3/11 in his professional role as a bowler in Bangladesh's first innings.
Cliff Young. One day, this Australian potato farmer showed up at the 550-mile longSydney to Melbourne Ultramarathon. Wearing overalls and rain boots, Young shuffled off the line while the highly-trained, corporate-sponsored distance runners left him in the dust. But Cliff Young had two things on his side: one, his goofy running style was actually very efficient; future race winners would adopt his technique. Two, he had no need for sleep. He completed the five-day run without stopping to rest, crushing the field of super-athletes by 10 hours. By the way, he was 61 years old.
The Autistic Psychic Savant class in Palladium's Beyond The Supernatural game pretty much has to be this trope. Most of the time, they can barely communicate, but in the presence of supernatural evil they prove to be smarter and more powerful than anyone else.
Jerry-R-Igg, one of the characters in the Paranoia Second Edition sample adventure, is a total coward, constantly freaking out at the slightest thing...while anyone's looking. Truth is, all of that's a front. As soon as he's sure nobody can report it back to the Computer, he becomes Captain X-Cess, standout in Deth Leopard and lover of Stuff Blowing Up (one of his possessions is a set of explosives disguised as snack food).
Leaf Coneybear from The 25th Annual Putnam County Spelling Bee is an airhead until he is asked to spell a word, at which point he turns into a scary blinking robot and gives the right answer.
Bark in Tick Tack is a complete doofus and the butt of numerous jokes, but apparently he's actually a powerful and decorated soldier.
Taiga in Fate/stay night is a silly Sensei-chan who spends most of her time at the house of one of her students, begging for food. When a random girl shows up, apparently freeloading, Taiga demands they duel for Shirou, at which point it is revealed that she is a world-class kendo champion. However, her opponent is a knight from the middle ages who lived and died by the sword, and was considered one of the best sword fighters in the world in an era when everyone was a sword fighter. Taiga gets disarmed in under a second.
Taiga: SOME STRANGER TOOK SHIROU AWAY...!
Subverted with Arthur Williams in Survival of the Fittest, who shoves aside his shyness and fear, charging an armed player in order to save a hostage, and gets shot in the face for his trouble. Paul Smith, also from Survival of the Fittest is usually a Chivalrous Pervert, pretty goofy and laid back — very much a comic relief character. However, from time to time, he almost seems to "switch on" and become one hell of a lot more dangerous. And try lethally dangerous.
Essentially the entire core cast of Mega64, but special mention should go to Sean and Horatio. Do not make them mad.
In Red vs. Blue Caboose is usually a complete idiot who loads his gun with crayons and keeps killing his teammates, however in episode 40 Caboose thought about everything that made him angry (spiky kittens, Red bull and Babies) and was able to kill every single one of the flag obsessed zealots in about 10 seconds.
This also happens to Tucker. He's as useless as anybody else until he gets his sword and, even then, he only shows brief moments of competence. However, in the final few episodes of the Blood Gulch Chronicles, he manages to defeat Wyoming and Gamma, quickly becomes a master sniper, and actually proves to be a pretty good leader for the blue team (a job which he was too lazy to accept previously). By the time he reappears in Recreation, he's mastered his sword as well and is able to destroy C.T.'s Warthog with one well-timed swipe. At this point, he's one of the most competent non-freelancer characters in the series.
All without losing his ("Bow Chicka Bow Wow") annoying/endearing original personality traits.
Not to mention going toe to toe with Tex, Maine, more Texes, and now running through an active battlefield with no cover, cutting down soldiers and not taking a single hit. At this point, the "non-freelancer" part is redundant. He's one of the most competent characters in the series.
As the series progresses, all of the Blood Gulch Crew end up becoming this. They were the lowest grunts of the UNSC military, constantly bickering with each other and deliberately kept away from major conflict, and thus should be completely unprepared for the super-soldiers and conspiracies they encounter. Except they repeatedly defeat them - with quirks and all.
Homestar Runner is one of the most idiotic characters to hit the internet. In "The Strongest Man in the World", he bicycle kicks the Cheat, while upside down, into the far horizon.
In 4 Branches, it's mentioned that Homestar's stupidity occasionally reaches such heights that it "flips back to start", and shows him answering the calculation "2 + 2" by defining Coulomb's law. When this is pointed out, he reverts to normal, revising his answer as "22".
Linkara from Atop the Fourth Wall is a nerd who reviews comic books for a living. He also has the power to manifest, invent, or contact any fictional person or thing. His standard weapon is his magic gun, but he's also found often using his Power Rangers Morpher, a Star Trek phaser, the giant robot death machine Neutro, a Pokéball with Pyramid Head in it, and several other things. He has used this to defeat Vyce, a Multiversal Conqueror, amongst other enemies.
Paul of LoadingReadyRun. Ridiculously techy, he can make anything from time machines to nerf rocket launchers from the junk in his garage.
Rebecca Stone from Demo Reel comes off at first as a ditzy Cloudcuckoolander with no empathy and no clue how to look after pets. Turns out? She's a Gun Nut security guard who won't hesitate to beat the shit out of anyone who hurts her best friends.
As of the 3rd November 2009, Boris Johnson. Normally poked fun at for always saying and doing the wrong things, the London mayor took a level in badass when he saw a woman on the street under attack by a gang of teenage girls; charging in to intervene, he picked up an iron bar one of the girls had dropped and chased them down the street on his bike.
The Cast Members at Disney World. A bunch of employees in funny outfits who, by the admissions of the "Jungle Cruise" operators, couldn't get into college. On 9/11, they evacuated the entire park. In 10 minutes
There's a reason you rarely hear about deaths in an amusement park where most of the visitors have put their brain on hold and many of the attractions involve complex machinery - safety is Disney's number one priority.
Pigeons. The little bastards can dodge hawk attacks. (Most of the time).
African Wild Dogs. They come in splashypatchworks of black, white, and tan, sometimes resembling clowns with their big, goofy ears. Their hierarchy is submission-based and packs are very close-knit, which results in lots of silly puppyantics. Compare this description with the fact that they have an 80% kill rate for hunts - for comparison, lions, aka the King of Beasts, average a measly 30% success. Who's top dog now?
Corgis. The little dogs the Queen of England keeps as pets. They used to be used for cattle herding. They responded to being charged by a bull by biting it on the nose. A small bull weighs roughly the same as 30 large corgis.
Most dog breeds when they put into their natural element for their breed. Great Danes that don't know their own size are for boars. Weenie Dachshunds are for badgers, the animal that lions avoid. All terriers are to fight one on one in cramped dark tunnels. St. Bernards and other mountain dogs for search and rescue under avalanche and blizzard conditions. Etc.
Giant anteaters have been known to kill predators like jaguars.
Though this is mentioned in the Cracked article above, the hippopotamus deserves a special mention. Chubby river dwelling creatures that look like they couldn't hurt a fly, right? Wrong. The hippo is widely regarded as one of the most aggressive animals in the world, and one of, if not the most dangerous creature in all of Africa, a continent second only to Australia in Everything Trying To Kill You-ness. Steve Irwin, a man who called himself the Crocodile Hunter, considered crossing a river filled with hippos to be the most dangerous moment of his career.
Cracked: There's this word, "territorial," that nature takes pretty seriously. When it's applied to a two-ton animal with teeth the size of bowling pins, that is one hell of a word. The sort of word you either pay very close attention to, or ignore and end up with a complimentary "Killed to death by a fucking hippo" tombstone. That sort of thing is really embarrassing for the family, you know?