Another example would be when Nagasumi grew giant after taking a mermaid drink and rampaged around without Magic Pants, one method of attack used against him was crashing a submarine out of the ground and RAMMING the tip into his...well, you can guess where this is going.
An unfortunate case of a doctor getting this treatment occurs in Magikano.
In the H-Manga Blue Eyes the main character Tatsuya orders a dog to sic on a would-be-rapist. The dog goes for the obvious weak spot.
In Dragon Ball Z Kai episode 65, Android 18 does a knee to the 'nads to Vegeta, likely her CWA. Better yet, she does it once he's running out of energy, which means that it's not really necessary (not to mention she's already much stronger than him anyway). She just wants to humiliate him with it.
Dragon Ball GT features the rare Double Groin Attack, where the main character kicks one groin while elbowing the other. Superb technique.
Vegeta: He keeps kicking me in the dick! Why?! Why does he keep kicking me in the dick?
Garlic Jr. gets one in the first movie courtesy of Piccolo.
The original Dragon Ball series! Yamcha was unlucky enough to get an especially painful one during the World Tournament. And from Shen aka Kami possessing a random passerby's body and making him a Badass Normal for a while nevertheless. Poor, poor Yamcha. Normally groin attacks are grounds for immediate disqualification in the Tenkaichi Budokai, but the judges ruled it was an accident (Yamcha went for a jump kick, Shen ducked, and groin hit head) so Shen was allowed to continue fighting, although only after Yamcha was given enough time to recover.
This happened to Mister Satan once as well. He landed crotch-first on something pointy... ouch.
It also happened to Gohan in the Dragon Ball Z Episode 251: The Old Kai's Weapon, thanks to Super Buu after he absorbed Gotenks and Piccolo.
Arale headbutts General Blue in the groin in Dragon Ball.
A gender-inverted one happened to Chi-Chi in Dragon Ball. Although it doesn't appear painful, while Goku and Chi-Chi (as kids) were flying on the nimbus, Goku (lightly) kicked her in the groin to see if she was a boy or a girl. Chi-Chi then pushed him off of the nimbus as a result.
In Dragon Ball Z: Resurrection F at one point during their fight after he has reached his ultimate form Frieza flips Goku over and knees him in the groin.
When Tagoma boasts that being Frieza's sparring partner for four months has made his body harder than steel and sophisticated attacks have no effect on him... and Gotenks promptly headbutts him right in the Dragon Balls (likely the one place Frieza did not attack him in those four months), for devastating effect. Roshi promptly states it wasn't a sophisticated attack.
Goku kicks Jiren in the groin to get a slight advantage.
In episode 89 Yurin kicks Master Roshi in the groin for looking up her skirt after he knocked her on her back.
Bel in Haré+Guu delivers one to Asio after he points out her lack of attentiveness. When she attempted it later Asio blocked it.
Fairy Tail: Lucy had been captured and is being held in the Sky Prision. After the Phantom Guild's master, Jose, is finished taunting her, she says that she has to go to the restroom; Jose, actually being pretty smart doesn't fall for it. Instead, he simply points to a bucket that was sitting in the cell and says "Go ahead." thinking she wouldn't degrade herself in such a manner, being the daughter of one of the richest families in the world. She proves him wrong and, much to Jose's surprise, goes to use the bucket. Jose, being a "gentleman" turns around so as not to watch and Lucy takes advantage of this and delivers a swift kick to his nuts and bolts.
He even does this against mecha, as seen when he shoots the Behemoth between the legs. In this case though, it's justified, since that's where the thing's cooling system was located and Sōsuke was trying to force its Lambda Driver to overheat and shut down.
Later on, Nico Robin performs a long-distance groin-grab on Franky in order to recruit him to the crew. Everyone else, men, women and children, react to this with appropriate horror. To quote a random female bystander, "I feel sorry for him...but he's still a pervert." What makes it even funnier is while she makes this attack, There's a sequences of repeated reactions with people saying something like "She's got him by the-" and then there's an insert shot of a piece of fruit.
Apis, while trying to escape from the Marines who kidnapped her, accidentally kicks a soldier in the crotch. The poor guy stood absolutely motionless after that.
During the Alabasta arc in the final battle Nami does this to poor Usopp who gets hit with both a stick and an explosion to blast Chopper and Vivi to the top of a clock tower where a giant city buster bomb is located.
Holdem, a subordinate of Kaido in Wano, has eaten a SMILE devil fruit which has made a Lion's head and arms grow out of his torso. The lion has mind of its own, and when the man and the lion disagree the latter tends to hit the formers balls in a fit of anger; nevermind the fact he that since they share the same body the lion is hurt as well.
Get Backers: Sweet little blind violinist Madoka Otowa does this to one of the guys who are holding her Stradivarius captive. In the dark. It's mostly off screen, as we only see her smiling brightly, then the guy hopping up and down in pain, but still...
Gintama has plenty of these. Gintoki falls victim to them the most, which might be related to the fact that the title of the manga is partly named after him and is only a letter off from being the Japanese word for the abused body part in question.
One of the "tricks" Kagura teaches Sadaharu for a pet show has him knock Gintoki and Shinpachi down, then stomp on their groins. Repeatedly.
Domestic Violence, the signature move of the Gintaman manga's titular character, is one of these taken Up to Eleven.
Gintoki actually gets his balls knocked off by a particularly brutal one during his bout in the Shikigami tag-team death match. They then proceed to get abused even further when Doman and Seimei decide to have them battle by taking control of them and ramming into each other before they finally end up getting crushed into a bloody pulp by Gedomaru in response to him asking her to make it stop.
In one episode of The Tower of Druaga: The Aegis of Uruk, Coopa is changed from a girl into a boy as a result of a magical trap. In desperation, she hits herself in the groin... with very painful results.
An example of the very rare female form of this occurs in The Tower of Druaga: The Sword of Uruk, when Ki does it to Fatina with a spoon. From Fatina's reaction, Ki did hit the right spot.
Kon in Ichigo's body gets one from Rukia, with him lying on the floor, apologizing to Ichigo for having it so that Ichigo won't be able to have kids anymore.
Played straight in the anime, where Ganju Shiba does the "lift his legs, repeatedly stomp" variant to Ichigo during their second fight after they meet again.
Tessai used this particular maneuver to punish Jinta for slacking off (or was that Jinta imagining how Tessai would punish him?). In the anime at least it absolutely happened as Jinta's flashback only occurs after Ururu reminds him of it.
After rescuing Orihime from Grimmjow, she asks Ichigo if she's too heavynote he's got her slung over his shoulder and he tells her "You're not as heavy as I figured". In response to this, Nel punches Ichigo in the crotch for being rude to Orihime.
Anime episode 207. Lieutenant Hiyori Sarugaki of Squad 12 tries to knee the squad's new captain Kisuke Urahara in the groin because she's seriously annoyed by his personality. Unfortunately it ends up backfiring on her: he wears some kind of hard protection (or else just has Balls of Steel) under his clothing and she ends up being the one in pain, hurting her knee. She later tries to do it again but stops at the last moment, recalling what happened the first time.
Anime episode 226. Captain Soifon tries to hit her annoying lieutenant Marechiyo Ōmaeda in the face but he blocks the blow and taunts her. She then hits him in the 'nads.
A flashback scene in Glass Fleet shows then-teenaged Cleo resorting to grabbing and squeezing in order to win a fight with another boy. Previously, Eimer also used the standard groin kick to stave off Attempted Rape at the hands of a group of prisoners, but that wasn't played for as much comedy.
Several transgendered variants show up in Ranma ½:
The standard Groin Attack was used, albeit unwittingly, exactly once: Ranma's ankles are tied to Akane and Shampoo's, respectively when they try running down separate corridors. Ranma, stuck in the middle, is pulled straight into the the corner (though he hits his head and his torso at the same time).
In episode 38, angry that Genma landed in his panty collection, Happosai responds by kicking him in the groin and knocking him unconscious with a blow to the head.
In episode 104 Sasuke attempts to abduct Ranma while he's in female form when he's sleeping. He starts to tie up his arms when suddenly his leg shoots up and knees Sasuke in the groin.
In episode 140, when Ryoga defends Akane from Happosai's six devils and they gang up on him, the centaur one headbutts him in the crotch.
The Reborn! (2004) anime uses this in the second episode for cheap laughs. Apparently Tsuna failing at playing volleyball then suddenly doing well wasn't entertaining enough: he had to start playing volleyball with his groin. And so, Reborn is an asshole as usual.
Someone made a Demotivator poster of one of these occurrences, with the caption, "Telling your girlfriend she has small boobs comes at a price."
In School Shock, Liu Li mistakes a peeping tom/Stalker with a Crush as an opposing military operative and attempts to get information on who he works for through torture. Naturally, the kid doesn't work for anybody so she decides to learn all she can through an interesting technique she saw in a film recently. After wrapping a ball in the end of a cloth, she swings it directly at the guy's groin and we see an egg crack and a Scream Discretion Shot. Later he's seen passed out.
In Toradora! Taiga delivers one of these to her own father. To be fair, though, Aisaka-san was a major Jerkass to her.
In fact, Yahiko invented a technique in the Jinchu arc called "Kamiya Kasshin Ryuu: Curse on the Descendants" which is essentially a flying sidekick to the groin.
He bit a guy in the groin in the manga. In the same chapter in which he was introduced.
Episode 17 of the Anime series had the Girl of the Week Marimo kicking the episode villain's henchman in the groin from behind as she and Yahiko were confronted by them while making their way back to the circus show. It's no surprise that the henchman was hopping up and down in excruciating pain while holding his crotch after Marimo's surprising kick and that both Yahiko and the villain were quite surprised to see such an event transpire.
At one point in the manga, Yahiko isn't watching where he is going... and walks headfirst into Sanosuke's groin. It Makes Sense in Context: Yahiko is really short, and by contrast Sanosuke is the tallest of the group.
Happens most unexpectedly in Chapter 41 of the Ga-Rei manga when Kensuke goes to check on Yomi, and quickly regrets it.
In Zatch Bell!, the melon-chomping V-shaped Victoream has shiny balls on his arms, either side of his head and at the tip of his V. When he gets tied up after his "Very Melon" song, Tia stomps Victoream repeatedly on the tip of his V, leading him to remark in the Japanese version "Don't bully my gentleman!"
An early chapter has Setsuna attempt a variant of this which is too horrible to describe, especially since she does it in a furo...to her ten-year-old teacher. And they're both naked. Cue Blank White Eyes. At least she had the excuse of not knowing that it was him and being scared off when he got in the bath.
Setsuna: Eh... um... this... I mean... well, to aim for a vital spot is basic theory and... I'M SORRY SENSEI!
There's also Haruna's imagined punishment for her (female) friends for keeping up The Masquerade against her; she illustrates it to them with manga pages involving them hanging upside down, panties exposed.. and Haruna has a whip and a good sense of where to aim... immediate genuflection follows.
Setsuna herself is subjected to one over 200 chapters later, courtesy of Evangeline. Also seehere.
Episode 6 of Slayers NEXT had Martina place a curse on Lina, in which any pain she inflicts on others is magnified and directed back at her. Naturally, she ends up kicking Gourry in the groin after he had accidentally grabbed her breasts (courtesy of Xellos) and made a remark about how small they are and...well, Hilarity Ensues.
Episode 14 of the original City Hunter had Saeko kidnapped by members of a local gang who's abducting beautiful young women. In her prison cell, Saeko gains the attention of a nearby guard and upon distracting him through the use of her sweet talk, Saeko kicks him in the groin, managing to get the cell keys from him while playfully apologizing about her deceptive kick.
At the beginning of the original series' Episode 43, the Girl of the Week, Utako Yumeno, knees a man in the groin from inside a train after he had suddenly bumped into her and accidentally looked down her shirt.
In the manga a punk once tried to kick Ryo there. Ryo immediately hardened his Gag Penis, breaking the punk's foot.
The first episode of the Dirty Pair Flash OVA series had Yuri kicking a leading police officer in the groin after he began to harass her about an item that she had gotten from a recently deceased man. It's safe to say that his teammates weren't too pleased to see this and that they eventually went after Yuri, who somehow got Kei involved in the chase as well.
The eighth episode of Burn Up Excess had a giant Rio dealing with a giant male transvestite as the two of them were battling in the city from within a Neon Genesis Evangelion-like parody battle. Near the end of the fight, Rio ends up delivering a devastating back mule kick to the guy's own groin and you can't help but feel sorry for him, since Rio (a trained martial artist) struck him with a sharp high-heel shoe and that you could hear the direct Sickening "Crunch!" of the man's own crotch (complete with an x-ray that shows the entire pelvis cracking itself). It's safe to say that it's gonna be a long time before the guy is able to recover from such a strike.
Episode 19 of Trigun had Meryl delievering a swift groin kick to a random Mook who got close to her after hearing something about a typhoon (which was possibly a reference to Vash the Stampede).
Episode 26 of MÄR had Jack winning his rematch against Pano through the use of some hallucinatory toadstools that made Pano see Jack as being some sort of handsome guy. When the effects had wore off, Pano was less than pleased about Jack manipulating her normal senses and she ends up kicking him in the family jewels, much to Jack's dismay and to his own teammates' embarrassment.
The third episode of YuYu Hakusho had Yusuke (in his ghost state) taking control of an unconscious young teenage schoolgirl's body so that he can protect Kuwabara who was on his way to school. During his fight against the school thugs that had tried to attack Kuwabara, Yusuke (in the body of the schoolgirl) is able to battle and defeat each of them with no problem and in the end, he delievers three groin kicks to the last thug before knocking him out with a hard right punch. Afterwards, Yusuke leaves the body of the young teenage schoolgirl, who is quite shocked to see on what has transpired.
Hunter × Hunter had a secondary female character who could Mind Control people after kissing them. The scene where she demonstrates her ability has her kissing a prospect partner, then making him lay on the floor and have her pressing her (heeled) foot to his crotch. Repeatedly. As the guy begs for more and she lets out a shrieking Noblewoman's Laugh.
Kurapica [touching his lips]: Whew... I was lucky she didn't choose me.
The second episode of Bastard!! (1988) had a ninja master named Gara infiltrate the castle of where the protagonists were currently staying from. Upon entering into the room of where both Luche and Yoko were sleeping in, Gara is quite surprised to see that Yoko is able to detect his presence and that he decides to introduce himself to her in an instant, but Gara is immediately cut short of his own introduction speech when Yoko throws a quick back mule kick to his groin from within an unexpected and surprising manner.
In one episode of Crayon Shin-chan, Shin's little sister Himawari has just had a cup of juice and wants more, but her mother Misae won't give it to her. Desperate and determined, she tries with all her baby might to reach and open the refrigerator, where her beloved juice awaits. After she utterly fails and exhausts herself, Shin-chan comes in from playing, sets up a chair in front of the fridge, and helps himself to the juice. An enraged Hima charges him like an angry bull, and headbutts him in the crotch with enough force to send him flying out the door.
A rare female example in the Abashiri Family OVA (created by Go Nagai), when Kikunosuke was fighting Mademoiselle Honey (Cutey Honey's predecessor), she kicked Kiku in the crotch (at 8:20 of the clip), and from the way Kiku reacted it must've hurt.
In the first episode, Fuu kicks a random guard in the groin while he was distracted by Fuu's pet flying squirrel, Momo.
Mugen gets one of these when he comes on too strong to an female undercover ninja (to be fair, she was undercover as a prostitute). This backfires, as after he crumples to the floor he gets back up and declares that he likes a girl with spirit.
In the last episode, Mugen is holding the bad guy in this weird upside-down wrestling hold, and if you look close, he's also biting him in the crotch. Call it badass or Squick, but remember that Mugen is at heart a Combat Pragmatist.
In the first episode of Mezzo DSA, Mikura kicks a Mook in the crotch with a clean kick. The visual metaphor of two gold balls shattering to dust is seen before the poor sap goes flying through a wall.
In Beelzebub, Oga, the main character, is surrounded by some of his high school's strongest brawlers, who challenge him for carrying a baby on his back (the baby in question? The son of the devil, sent to earth to learn to be evil from the most evil human alive, Oga, while he grows up, but they aren't to know that.) Oga's response? The first two that attack him both get an instant punch to the groin as he walks past them. In a later chapter, when a policeman threatens Oga with the law, then turns around, Oga kicks him in the crotch hard enough to lift the policeman up.
Maylu actually kicks Tora in the crotch when he harasses her in the MegaMan NT WarriorManga, causing him to fall to the ground in pain. Could've been better, tho...
Almost to the end of the second episode of Puchim@s, Afu runs toward Mr. Producer, leaps up... the top of her head slamming into his crotch. Immediately, his legs wobble and buckle before he falls down on his knees.
In Sonic the Hedgehog: The Movie, towards the end of the film, Sonic falls onto the upraised prow of a hover-ship crotch first and promptly starts reacting in silent pain. Robotnik is baffled by Sonic's antics, then notices that Sonic's robotic doppelganger (which has embedded itself in the hover ship's underside, so its head is sticking out of the floor) is getting kicked in the head by Sara, who's accusing it of trying to look up her skirt, and claims that Sonic must be trying to synchronize with Metal Sonic.
In Sonic X, when Emerl goes berserk in the Sonic Battle arc, Sonic tries to fight him off, as Emerl issues one of these onto Sonic. We then see everybody's horrified reactions. Made even funnier when Sonic tries to take it like a man (err, hedgehog) despite being in immense pain and his voice getting higher. He faints anyway. Surprisingly, 4Kids left it in, but unsurprisingly, they found another way to work around it.
In episode 4 of Baki the Grappler, when Baki is fighting (and losing) against The Beast of Yasha Crag, he tries a groin kick against the ape, which he finds to be effective. He then continues to kick the creature repeatedly in the genitals as hard as he can until it finally throws him away.
In episode 15 of Dragon Quest: Legend of the Hero Abel AKA Dragon Quest I - Yuusha Abel Densetsu, Mokomoko (also known as just Moko), the rotund, hairy barbarian, falls from a great height, and he lands groin-first into the open jaws of a sea creature, with its fangs pressing against his crotch. There is a funny 'boing' sound, and he flails his arms around with a pained expression.
In Bio-Meat: Nectar, Maaya executes one against a school bully in the beginning of the manga. "As far as I'm concerned... YOUR DICK IS REVOKED!!"
Also in the beginning of the manga Doctor Slump, Arale punches inventor Norimaki Senbei (her father, or better said, her creator), nearly caving his nuts in!
Senbei: A LITTLE MEANS A LITTLE AND NOT WITH FULL POWER!
Episode 15 while training Sadaharu (the giant dog) for a show, he crushes Gintoki and Shinpachi's crotches. Kagura cheers him on ...
The chapters involving the warring Ketsuno and Shirino clans dealt massive damage to Gin's tama. And then after they fell off, each one was used by the clans to fight against the other one. They even got individual names.
Yu-Gi-Oh!: When the gang rides a helicopter to Dartz's lair, it bounces around in a storm and Mokuba ends up flying headfirst into Tristan's groin, flooring him with pain. 4Kids edited it so Mokuba flies into his stomach instead.
In Yu-Gi-Oh! GX, when Dr. Crowler dueled Bonaparte, Bonaparte's monsters fire their cork-loaded shotguns at Crowler's groin. This occurs twice during the series run. Surprisingly, 4Kids kept the shots in.
Action Girl Fabiola does this to a thug during her first visit to the Yellow Flag...with a blade built into the heel of her shoe. OUCH.
Surviving this and other painful hits is what marks Rotton the Wizard as Made of Iron. More exactly, he may be a Love Freak of sorts but he was smart enough to use protection... there. Good thing, too, as he faced someone strong enough to dent said protection (namely, Roberta in full Ax-Crazy mode during the El Baile de la Muerte arc), but at least it did its job.
In episode 22 of Nekojiru Gekijou, Nyako kicks a fish in the crotch while Nyatta smacks him across the head with a plank after he hits them.
In chapters 55-56 of the manga, Seiji enters a female wrestling competition in hopes of winning one million yen. He and another contender named "Helter Skelter" make it to the final match, but "Helter Skelter" aka his sister Rin knows his true identity and immediately begins to disarm him with repeated kicks to the crotch, prompting some rather amusing commentary from the emcee.
Emcee: Good thing this is women! If she was a man, she'd be dead by now!
While losing consciousness, Seiji manages to pull off a Cross Counter, knocking "Helter Skelter" out and winning the match. But while leaving the ring, "Helter Skelter" also leaves with a loose thread from Seiji's pants. Hilarity Ensues, especially when Seiji tries using his right hand to cover himself. Needless to say, he was disqualified.
Kekko Kamen inverts this trope rather humorously: instead of an attack TO the groin, Kekko Kamen's finisher, the "Open Thighs Jump", involves an attack WITH the groin, as Kekko Kamen presses her nether-regions against an enemy's face to finish them off while they're distracted by her nakedness.
Played straight once, as Kekko Kamen's opponent was a woman who countered the Open Thighs Jump with a chop right there.
Played With in Chapter 29, Kosukegawa is bitten in the crotch by a viper and passes out. Panicked Tsukishima, Fujiko and Hino strip off his shorts in order to Suck Out the Poison... but then they notice he doesn't have any bite marks on his manhood, as the viper actually completely missed him due to his small size only managing to bite his shorts, and Kosukegawa only passed out from the shock. He wakes up moments later, pantless with all three girls staring at commenting on his Teeny Weenie and has a massive Naked Freak-Out.
A quite gruesome (but still funny) example. While fighting Hibiki, a yakuza member has his junk sliced down the middle with a katana. Hibiki is convinced to apologize to him in the hospital, but the gang member responds with threats and abuse. So Hibiki flashes him, which just makes the damage worse.
Hetalia: Axis Powers: In the first episode of the World Series Canada and America play catch and one of the balls America throws hits Canada... there. Since America has Super Strength... OUCH!
One chapter has Black Star training in hand-to-hand combat with Patti Thompson. He insists that he needs to have his hands tied so as to make it a fair fight (against the girl who's beaten the rest of the class). Unfortunately, he turns around to have this done when the fight had already begun. Cue Patti gleefully kicking him in the crotch.
In the Anime, after he finds Angela and goes on a victory speech, she kicks him between his legs.
In the manga, after Dressing as the Enemy, Soul and Kid are assigned to babysit Angela. Five minutes in, she whacks Soul in the crotch with her broomstick. Finding his reaction funny, she decides to make a game out of it and does the same thing to Kid.
In his fight against Masamune, Black Star runs circles around his foe and taunts him, but eventually slips and flies groin-first into a pole.
The manga volumes include a chapter where Lupin "teaches" a young woman to defend herself from attack by slapping her hands together on top of the... male sex symbol. (The manga's replacement for genitalia)
In episode 10 of Lupin III: Part 1 series, when Flinch aims a second kick at Lupin, he catches it and kicks Flinch in the crotch.
In the Lupin III: Part II series, he has used this tactic to escape from a large police officer who had him in a hold.
Attempted in the Rumiko Takahashi short film Fire Tripper; when Shukumaru takes a glance at Suzuko while she is bathing, she grabs a large rock and chucks it Shukumaru, landing inches away from his goods.
FLCL episode 6 "FLCLimax". In the manga style sequence Haruko kicks Naota in the crotch.
Pocket Monsters has a truly horrible variation. Red makes a comment about "balls" which causes Blue to check his pants, thinking he's talking about Pokeballs. He pulls his testicles, though it's in a goofy way that fits the Deranged Animation of the series (it comes out very long and stringy). This, obviously, causes Red much pain.
Played for comedy and as an actual make-shift attack in manga Blazer Drive. After finding the character known as Beast impervious to harm, main character Daichi swiftly slides his body between Beast's legs, facing up at Beast, who can only watch in terror as Daichi lifts his sneaker-clad foot and slams it, sole-first, into Beast's unfortunate groin. Beast then berates Daichi, saying that - as a hero in a shounen manga, he shouldn't be launching such dirty attacks. Daichi counters by pointing out Beast had requested he attack with everything he had, also making note of the reason for his attack's target - "That part is not hardened as well."
In New Testament Vol. 1 of A Certain Magical Index, Touma makes a Big Damn Heroes rescue at the end when everyone thought he was dead. Once the bad guys have been defeated, he starts to explain what happened to him... when Leivinia Birdway suddenly sneaks up on him and kicks him in the groin, calling him a moron.
In one episode of Eureka Seven, Renton and a drunk Talho are making their way back to the ship when they're attacked by a gang intending on raping Talho. They are then rescued by Holland who beats up the gang and holds the leader who was on top of Talho by his nostrils. Talho then takes the opportunity to kick him in the groin as he's pulled off her.
In Ixion Saga DT, Kon is smart enough to stop Erec with a Dragon horned toe boot wearing foot to the groin. The damage to one of his testicles was so severe the doctor was forced to remove it. Their next encounter has Kon smashing his groin once more, this time with a ROCKET HAMMER, costing him his other one!
In "The Double Trouble Header," Casey's Ratatta hits James in the groin.
In one Johto episode, when Ash sends Bayleef to Professor Oak's lab, Bayleef panics and runs around, and she eventually rams into Oak's groin.
In one Sinnoh episode, when Brock flirts with Nurse Joy, Croagunk poison jabs Brock in the groin.
In the second episode of Xam'd: Lost Memories, a smart-mouth crewman pisses off a little kid... and the kid slugs the big jerk right in his twig and berries!
Turns up again and again in Gu-Gu Ganmo. The main character Hanpeita's sister kicks him in the crotch to wake him up every morning (one episode revolves around his attempts to get her to stop). The methods get gradually harsher as the series progresses, starting with "denki anma" (applying pressure and vibration to the groin to cause discomfort) and progressing to elbowing, stomping, and a succession of full-force kicks. Hanpeita and others fall on their crotches with some freqency, and at one point Hanpeita has a running hairdryer and a hot towel shoved down his pants in the space of two minutes. Ganmo is shown to be immune to groin attacks, but hitting his comb produces similar results.
In episode 6 of Panty & Stocking with Garterbelt, an underground explosion causes fire to spray out of all the toilets and urinals in the school, burning everybody who was using them.
In volume 2 of Air Gear, Ikki is spying pervily on Simca while she finishes her shift in the skate shop. Mikan then decides to interrupt this with a solid boot to the family jewels (and in the manga, they even make a sound like metal being hit). Predictably, he then engages in a bout of silent screaming.
And then, the series takes it Up to Eleven...with a water bottle.
In Campione!, Godou acts as a baseball catcher and takes a baseball to the groin.
Hanjuku Ninpouchou features the occasional groin kick up until Volume 5 when Miyuki begins whaling on Raita's balls seemingly every other page.
Anna from Shaman King promptly kicks the soon-to-be GOD, and gets herself quite a reputation for it.
In Nozomu Nozomi the recently gender bent but still hiding it protagonist takes a line drive to the crotch while playing baseball and discovers that it does indeed hurt to get nailed in your girl parts and the usual techniques boys use to deal with the pain either don't work or would give away too much. It's more worrisome when Nozomu's best friend Yasu playfully mimes an "electric breaker" wrestling move (with more of a squish than an actual stomp) while they are roughhousing and notices Nozomu's crotch doesn't feel right underfoot. He almost uncovers Nozomu's secret before another teammate distracts him.
The use of the Turn A as the victim also serves as a Mythology Gag, since Turn A's protagonist Loran took a few hits to the family jewels himself, most famously jumping from one airplane to another in mid-air and landing groin-first on the fuselage.
In Yu-Gi-Oh!: Capsule Monsters, after escaping a nest of baby Duel Monsters, Jounouchi crashes into a tree growing out of the cliff groin-first.
As it's a series with Japanese Delinquents as the protagonists and most of the cast, groin attack appear rather often in Kyou Kara Ore wa!!. The most epic one was the one Mitsuhashi used to defeat a bear, without ever being told it was actually a man in a suit trying to scare him off.
In You and Me a kindergartener once kicked Kaname in the groin.
Tsukamoto from DAYS gets hit in the crotch with a soccer ball in episode 1.
Yukari Sahashi starts developing a habit for it in Sekirei. She's helping Shiina, the Sekirei she winged, find his "sister", Kusano,note She'd long found her Ashikabi in Yukari's older brother, Minato, but she doesn't know this. but she kept running into misbehaving young men instead, which she promptly dispatched with the trope, earning her the moniker "Demon Ashikabi".
My First Girlfriend is a Gal: Episode 10 of the anime shows Ranko Honjou kicking Dai Mitarai's balls when the latter tries to plead mercy, claiming that those who toy with women have no right to have them.
My Hero Academia: Midoriya was just being nice when he greeted himself to young Kota in the start of the Training Camp arc. Kota promptly answered his greeting with a full-force low blow, earning admonishment from Iida. This is played both ways: the attack is initially played for comedy but is later revealed have drama elements as well, as Kota has issues with heroes. Kota does later apologize for this through a hand-written note, however.
In preparation for the Grand Bout, Chrome trains in combat, but since he's got no talent for it he focuses entirely on striking below the belt. In this case he has extra motivation since his main opponent is Jerk Jock Magma, who's made it clear that he's willing to let the priestess Ruri die, if he doesn't just kill her himself (and Chrome has been in love with Ruri since they were kids). During their actual fight, Chrome uses Suika's vision-correcting helmet (plus his literal sweat and tears) to make a Solar-Powered Magnifying Glass to light Magma's clothes on fire, then "mercifully" put him out with a groin attack that knocks him into the lake.
In a later match, Ginro misinterprets a comment Ruri makes and goes full scumbag, trying to win the tournament so he can marry her and become chief. Senku, who has even less combat ability than Chrome, turns his staff into an impromptu lever using Suika's helmet that was still left in the ring from the Chrome vs. Magma bout, and nails Ginro in the soft-and-danglies.
Later in the story Chrome is captured by Tsukasa's Empire of Might but manages to pull off a jailbreak. The jailer Yo chases him down, but Chrome psyches him out with fake blood and lies about having pneumonia. While Yo is recoiling in fear, Chrome hits him between the legs with a bamboo pole and escapes.
In the 9th episode of Dirty Pair after a giant mook picks Kei and holds her in a lock, she gets free by kneeing him in the groin.
JoJo's Bizarre Adventure: Diamond is Unbreakable. During his fight with Josuke, Okuyasu reveals his Stand, The Hand, and its ability to erase anything on its path. That Okuyasu mainly uses to erase the space between him and his target so he can bring them closer and punch them in the face. Josuke turns this against him by tricking Okuyasu into erasing the space between him and a wall, causing three potted plants perched on the wall to fly off directly at him. The first one hits him right in the face, the second one in the throat and the last one goes straight to his 'nads. He's knocked out immediately.
A story in the second volume of Maboroshi Panty has Maboroshi Panty at one point attack the villain Waki by biting his prehensile penis.
The Rising of the Shield Hero: Motoyasu finds himself on the receiving end of a good kick to the crotch from Filo for making fun of her. Next time he sees her in her human form and (not knowing it's her) refers to her as a "fat bird". She quickly changes forms and kicks him on the crotch once more (and we learn he was wearing some metal plates down there for protection). Naofumi then orders her to do that every time they see him, which she gladly accepts.
In episode 14 at one point when Honey chases after Sister Jill she accidentally steps on Danbei Hayamas groin as he laid on the floor having been knocked out earlier.
In episode 22 while being chased by Danbeis big ape of a nephew Naojiro who intends to rape her, Honey whacks him in the groin with a baseball bat.
The girls in Shiritsu Yabasugi Gakuen are extremely fond of inflicting these - there are probably between ten and twenty in each volume of the manga. Nobody makes a big deal of it and (shockingly) nobody ever suffers a serious injury. Typically, the attacks fall into two categories:
The most common is a simple kick in the balls, usually in retaliation for sexist comments or behaviour.
In Hard Boiled Angel, the English translation of Korean police procedural manhwa Angel Dick, the lead character Lieutenant Jiran Ha is notorious for her frequent use of these:
She subdues several villains by kicking them in the groin.
In the first volume, she begins a "game" of hitting the office dork Detective Choe in the balls every time she sees him. This continues for the rest of the series. On the rare occasion he manages to avoid her punches and slaps, she gets him as soon as his guard's down. When he complains, she tells him that she has no intention of stopping, so he will have to either stay on his toes or learn to suck it up.
One of her colleagues offhandedly remarks that she once "kicked the Commissioner in the nuts".
Eikichi kicks Takezawa and Mitsuya in the crotch when fighting to save Shinomi from the Idaten.
Shinomi kicks Eikichi in the junk sometimes, when he's being especially lecherous.
In the manga, Gushing Over Magical Girls, Magia Baiser stakes Azul spread-eagle on the ground and starts stamping hard on her crotch while hopped up on dark magic in chapter 35.
Played for Drama
In Kite, Sawa kicked a bodyguard in the groin twice, causing him to vomit, and later shoots Akai, her rapist, between the legs.
In Perfect Blue, one of the murder victims is stabbed repeatedly in the groin with a screwdriver.
Kurz Weber resorts to a groin kick during his knock-down-drag-out fight with Guen Bien Bo near the end of Full Metal Panic!, but it doesn't give him the advantage for very long.
Chizuru Honda from Bokurano does this in a Humongous Mecha, to the other mecha she's fighting. Quite ironic, considering her status as a girl who got pregnant due to rape.
Momo of Peach Girl does this to Kairi's brother Ryo when he tries to rape her.
Episode 12 of Macross Frontier has Alto finishing off the rebel leader by stabbing his Powered Armor's groin with a knife. One could only wonder how much damage a knife that can penetrate power armor causes to organic tissue... Especially since both combatants are the size of mechas and the knife is sized accordingly.
In one episode of Yu-Gi-Oh! ZEXAL Yuma did this to Gauche when he and Droite tried to use muscle to interrogate him after Haruto was kidnapped. (This time the dub edited it out, probably because, unlike the case in Yu-Gi-Oh! GX it was not supposed to be funny.)
Used in Video Girl Ai, when Youta puts on a facade and assaults Ai to save her from Rolex's control. She reacts by squeezing his nuts until the pain makes him stop, and then she realizes what he was truly trying to do.
Present in Airmaster during the combat betwheen Minaguchi Yuki and Aikawa Maki.
In Eden no Hana, Midori applies one on her rapist stepbrother to escape from him and join her real brother, Tokio.
In Soul Eater, Death the Kid seemed to have no qualms about kicking Mosquito-from-200-years-ago between the legs during his fight in Baba Yaga's castle.
In Red River (1995), this happened to Urhi in the past. He's an eunuch, and hides this fact until people accuse him of being Prince Juda's real father, which technically is impossible since he was castrated before he met Jude's mother Queen Nakia.
In Berserk: The Golden Age Arc II - The Egg Of The King, Guts stabs a guard in the groin with his sword in half-swording fashion while fighting his way out of Count Julius' mansion.
Being a manga on Professional Wrestling (even if they treat it as real), Tiger Mask features them with a certain frequency. And the second-to-last story arc establishes that the tournament is filled with extremely capable heels when two of them react to a rather vicious one (it involved a chain and breaking the victim's groin cup) by calling it childish (Tiger Mask, who executed it, privately agreed).
Cynthia the Mission had this done to a girl. With a TOE BLADE. Kanae pops a blade out of her shoe and kicks Bridget in the crotch, and as Bridget was wearing a short pleated skirt, all that was between her vulva and the weapon was her panties, which the blade sliced through easily, plunging into Bridget's underparts, presumably into her vagina. Though not directly killed by this devastating blow, Bridget is, unsurprisingly, heavily incapacitated by it, and tries to stagger away, bleeding severely from her crotch.
Poor Inui in Shinjuku D×D. He gets one when a Yakuza decided to shove his gun in his crotch (thankfully he didn't discharge the gun), and another one from a different member of another Yakuza group with a taser.
The backstory of Juuzou Suzuya reveals that he's so androgynous because his "Mama" castrated him with a hammer to prevent puberty.
In a blink-and-you-miss-it moment, Shuu Tsukiyama's wanted poster mentions that he murdered and castrated a politician.
The sequel features the female Ghoul Ayu, nicknamed "Nutcracker" for her preference for stomping on men's genitals and slurping them up like oysters. One unfortunate Red Shirt suffers this fate, while Shirazu barely escapes with his goods intact.
Mutsuki does this to Takizawa, kneeing him and following it up stomping on his genitals. It's not only dirty fighting at its worst, but an early indicator of the trouble to come.
Played for both Drama and pitch black comedy in Thou Shalt Not Die where the group is coming under fire from a sniper. The first shot ends up costing Botan her hand, the second ends up hitting Mizukaki in the nether regions. What makes it comedy is the face he makes as it happens.
A blink and it's missed moment towards the end of the Another anime features the trope: Yumi slips when she tries to stab Mei while leaning onto a slippery window ledge, only to land crotch first on said window sill... and then to end up fallingto her own death.
In Dragon Ball Super, after upgrading his sword into a Laser Blade powered by the combined ki of everyone on the planet, Future Trunks splits Merged Zamasu in half vertically, starting at his groin. And he holds his sword there for several seconds before moving it up.
In Captain Tsubasa Rising Sun, it's revealed that Juan Díaz's reason to not have attended the World Youth Cup was this trope. During the Argentinian championship, he got kicked so violently near the crotch that his hip bone and cartilages were damaged so he had to be operated on and then hospitalized for several months, causing him to miss the WYC. He recovered well enough in the end, however.
When Meg is kidnapped at the beginning of Burst Angel, Jo sees fit to threaten this with a Desert Eagle on Kyohei, stopping just short of pulling the trigger. Share the Male Pain on that one.
In the anime of Wanna Be the Strongest in the World!, Digger and Hornet give a vicious one to Sakura in an attack that shows how dangerous a tag-team they are. They take Sakura and drag her crotch-first along the top ropes, which causes her to collapse and grab between her legs in agony. The pair then pick her up and headbutt her back and forth between each other, until she gets knocked out.
In YataMomo, The Old Homeless Guy reveals the reason his life spiraled out of control is because his wife castrated him (and presumably kicked him out) after catching him cheating on her. Despite this, they later make amends and get back together, allowing him to leave his homeless life behind.
In Devil Man The Birth after Ryo attacks the partygoers with a broken liquor bottle to spill their blood to summon the demons, they start fighting back and knock him to the floor, they then beat on him while hes down and a woman kicks him in the crotch.