Parodied in the episode "Conjoined Fetus Lady": After timid English doormat Pip is insulted by the Chinese dodgeball team, he wipes them out with a single throw.
Kyle in "Tonsil Trouble".
Subverted in Avatar: The Last Airbender: Like the G-Gundam example, Aang can gain superpowers through intense anger, but they're imperfect (and really hard to control) that way; he's supposed to trigger the "Avatar State" through meditation and Buddhism-like detachment. What's more, despite the power Unstoppable Rage gives him, he also risks being made Deader Than Dead if he's killed while fighting that way (normally he'd reincarnate). Also, in complete contrast to the result of the first season finale, the climax of the second season finale confirmed that even in this form, he is quite far from unstoppable. It did help that during the first season he was teamed up with the massively P.O.'d spirit of all oceans.
However, the final fight of the series has Aang regaining control over the Avatar State after it had finished tossing around a supercharged Ozai like a ragdoll in time to prevent it from killing him.
Not just that - he regains the use of the avatar state, and then subsequently achieving control.
Played straight in Avatar when Avatar Roku assists Aang and tears down a Fire Temple around the treacherous monks within.
Happens when Cat from CatDog snaps at a Monster Truck Rally.
Heroes and villains alike in Transformers tend to do this a lot, with varying degrees of success. Biggest, oddest example: In one episode of Beast Wars, a cybervirus that was supposed to turn Optimus Primal into a coward instead made him a berserker who smashed up the good guy base when they attempted to hold him back, then stormed the enemy base single-handedly.
Brock Samson from The Venture Bros. has a hair-trigger example of an unstoppable rage.
Ren Hoek of The Ren & Stimpy Show would fly into a rage whenever Stimpy would do something mildly annoying and often beat him. But if anyone else was involved, being a chihuahua, Ren was so weak that he was more likely to be beaten as a result of these than anything else.
Except for one episode, "Man's Best Friend" (which was banned from Nickelodeon in part because of this), in which Ren, bought by George Liquor as a pet/guard/show dog, is pushed to the brink, and proceeds to beat George to a pulp with a boat oar, laughing maniacally as he does it.
This happens again in the Adult Party Cartoon episode "Ren Seeks Help", in which, after Mr. Horse insults his sanity one too many times and threatens to kill him, he transforms into an insane wild animal and proceeds to beat the crap out of him and eventually beats him to death with his gun. Nothing could snap him out of it and he's sent off to an insane asylum, not before biting off one of the guards' hands.
Numbuh Three from Codename: Kids Next Door. Usually, she's a sweet, innocent, little girl, but when she truly gets angry, anyone who has known her for long cowers in terror, she develops Fireball Eyeballs and sometimes Scary Teeth, and enough raw power to beat up even Mr. Boss, a Big Bad Duumvirate of the series. (As seen in "Operation: M.A.C.A.R.R.O.N.I.")
Donald Duck. When people or animals have annoyed him too much, he's raged to the level of extreme violence, although he's always managed to stop himself before killing anyone. He manifests this trope to such an extent that he's often depicted with the features of a devil while in this state.
In "Cured Duck," he tears apart Daisy's (his girlfriend) house, even ripping out telephone poles because he couldn't open her window (it was locked).
In "Sea Scouts," he knocks out a shark with a single punch because it ruined his hat!
In "Donald's Double Trouble," he finds out his "double" is kissing Daisy in the Tunnel of Love and nearly destroys the entire ride!
"Donald's Penguin": The little penguin keeps trying to eat Donald's goldfish. Donald nearly blasts it out of the house.
"Donald's Rocket Ruckus": when the kids sneak on board the ride Donald is operating after Donald's readjusted the height requirements so they can't board, Donald gets so ticked he spins the ride out of control. It gets worse from there.
Toki Wartooth in Metalocalypse. With accidentally causing the death of his father, he was already pretty unstable. It's when a really annoying fan won't leave him alone at a concert that Toki finally snaps, beating the fan to death with his bare hands.
Kim Possible and Shego get tagged with emotion-controlling moodulater chips. The device control gets broken when it's set to "anger", leaving them locked in what the chip's inventor describes as "an irreversible frenzy of rage".
Buttercup will go into one of these if someone makes fun of her, threatens her sisters, or calls her cute.
The "threaten her sisters" part could be applied to all of them, as Blossom opened a can of whoopass on Princess after she knocked out Buttercup and Bubbles.
Bubbles in the movie went Trigger Happy with her lasers on Mojo after he grabbed Blossom and Buttercup and started trying to squeeze them to death.
Bubbles does this in "Bubblevicious" to prove to her sisters that she's not a baby.
In the pilot "Meat Fuzzy Lumkins", after Fuzzy's meat gun turns her pigtail into a chicken leg, Bubbles clobbers him.
In the "Low Tidings" episode of The Marvelous Misadventures of Flapjack, Captain K'nuckles is revealed to have had a traumatic childhood experience on Low Tidings Day in which a group of mermen stuffed him into a sack for not being a good person (as is tradition for all of the bad people in town). When K'nuckles plays the part of the "quiet boy" in a Low Tidings pageant in an attempt to be a good person, the other cast members have him stuffed into a sack for the same offense. Needless to say, the pageant was doomed from that point forward.
Audience Member: He has the strength of ten quiet boys!
In Ultimate Alien, Ben completely loses it after Aggregor killed five aliens and absorbs their powers. At one point, Humoungosaur throws a house at Aggregor, and gives him a No-Holds-Barred Beatdown. And yes, this is thatBen Tennyson!
The ones who you have to worry about are Beast Boy and Raven, who, when pushed over the edge, are capable of wiping the floor with Slade, who Robin could only match in hand to hand combat. Then again, what would you expect from pissing off a half demon or someone who can turn into any animal that has ever existed?
Robin will also go into a rage when compared to Slade, the Big Bad.
All of the Titans can be pretty nasty when pushed, which is proved in "The End Part I", when they go to all ends to protect Raven from Slade. Starfire can gather massive amounts of energy and unleash it in a big blast, Beast Boy apparently learned to turn into that man-beast thing at will and beat up anything, Robin turned his birdarangs into swords (a feature we see for the first and only time, and Cyborg turns into a walking cannon! He drains the tower's power supply to fire a massive blast at Slade and his army, very nearly succeeding, too. The Titans are not to be fucked with.
Sym-Bionic Titan: Lance does this after Octus is electrocuted. He ends up taking over G3's ship and let loose everything it had into the monster and the space station, vaporizing it completely. Even Solomon, who is just as Badass as Lance is, knew it was a good idea to stay out of his way despite the fact his ship had just been hijacked.
In the Peter Pan & the Pirates episode "First Encounter", when it appears that Captain Hook has fed Nibs and Toodles to the crocodile, Peter gets very upset. Hook mocks him for it; Pan then flies into a rage and attacks Hook more intensely than he had ever before, ending when he knocks Hook's sword out of his hands. Peter then uses it to cut off Hook's hand.
Mirta from Winx Club is referred to as creating "illusions powered by emotions". When the Trix try to kill Stella, Musa, Flora, and Tecna, Mirta rages out and conjures up a gigantic nightmare thing in front of them; not only does it scare the bejeezus out of Stormy and Darcy (which causes their spells to fail and free the Winx), but even Mirta gets a little freaked out by what she's done. Good thing she's a wallflower most of the time . . .
In fact, after the multitude of lesbian hook-ups, the post-first-season fanfiction storyline that was most popular was Mirta letting all her anger out and leaving huge trails of traumatized teenagers and scared-literally-to-death corpses in her wake; most of them had her only using illusions to accomplish all this.
Chimera, a minor villainess from Season Three, had a fearsome temper that made her magic stronger. Her only named spell used in the show summoned a huge storm, and was insanely powerful because she cast it in the middle of a monster rage-out.