In chapter 16, when Rainbow tries to calm her down:
Firefly: I CAN’T CALM THE BUCK DOWN!
In chapter 19, she does it for the third time, this time aiming it at Black Star:
Firefly: I DON'T GIVE A FLYING FEATHER ABOUT YOUR ORDERS!
Of all people, Nia calls Yoko a "bitch" in Tengen Toppa Gurren Solvernia. Because of a Love Triangle, and the fact that Kamina had died, Nia was completely broken and then Kiyal thought it would be a good idea to have them talk about their feelings, that they could support each other. Things went from bad to worse, really worse. But, after their discussion, both Nia and Yoko are totally remorseful of it.
A Growing Affection is over 650K words long and uses 'shit' exactly five time (the 'F' word does not appear at all).
1) Anko says 'Oh shit' in surprise when Naruto and Hinata walk into the restaurant where she and Iruka are having dinner (their relationship is supposed to be a secret from Naruto).
2) Kankuro's only thought is 'Oh shit' when his team is attack by the unleashed One-Tail.
3) Naruto says 'Holy shit, Hinata!' when she suddenly and unexpectedly strips down to some very sexy lingerie.
4) Kayo of the Grass promises to round up 'everyone who isn't a traitor or too chicken-shit to help'.
5) A random grey Shozoku proclaims 'Shit' when realizing her squad has fallen into the heroes' trap.
Address Unknown has Rainbow Dash's exclamation of "Bastard!", after learning how Derpy's previous boss put her on probation and then fired her at the first opportunity, over an accident that was actually Twilight's fault. She follows it up with an undescribedCluster F-Bomb.
There's also chapter 12, when the Grand Master Fangirl's evil plan has finally been revealed, and we get this:
"Well, now what?" Lexaeus sighed. "It would seem we are…" Vexen murmured. "Lost for options?" Xaldin suggested. "In a tight spot?" Lexaeus added. "Between a rock in a hard place?" "In hot water?" "Verily fucked," Vexen answered. "Ah."
If you can get the DC Nation universe version of Connor Hawke to the point of swear words, it's usually one of those.
For the most part, the Shocker fan fic Polarity avoids any swearing worse than "damn" or "crap." Even after fighting zombies, avoiding heroes, brawling with villains, and getting his ass handed to him night in and night out, Herman Schultz and company keep the language tame...until Big Bad the Grim Reaper shows Shocker what happened to the last guy who turned him down, revealing the Punisher trussed up like a stuck pig slowly being bled to death.
After my jaw dropped for a few seconds, I decided it was time to sum up this entire situation in a very simple and succinct phase. "You're fucking nuts."
In Pretty Cure Heavy Metal episode 24, Shugo fakes an Australian accent and lands a precision N strike in a parody of the N word privileges supposedly held by white Australians. The rest of the N words are spoken by the token black, who has all the N words in episode 25.
Later, in episode 51, Shugo drops an uncensored F bomb right before she dies from her wounds, just to maximize the impact. She gets better.
In Kira Is Justice: "Oh crap." Bear in mind that the author almost never uses any curse words in his writing. Not even "stupid".
In Relationships Series story "Pain", Shamal asks "what the hell happened" to a badly injured Yuuno. Vita notices that this is the only time she has heard Shamal swear.
Harry Potter: Draco nails this trope in Yea, Though I Walk when he explains to Hermione, that killing Snape won't stop the demon that is claiming the Death Eaters from possessing his body The cursing and Draco's grief due to mercy killing his possessed father in vain, and her mother sacrificing herself to the demon to save her son really highlight that the situation seems completely hopeless.
Draco: You can't kill a fucking demon with a pillow!
In another Harry Potter fan fic straight-laced Percy realizes that the Minister of Magic is under the Imperius curse, which could only mean Voldemort is controlling him. His mental response: "Oh, shit."
In the fifth chapter of thisDeath Note fanfic, Mello finds out that Matt scored a lot higher than he'd assumed. It turnes out the two of them made a Side Bet, with Mello assuming that he'd win. Well it turns out things didn't go that way...
Phoenix drops a pair of "Dammit"s through the story. It doesn't go unnoticed.
Phoenix: Dammit! She knows! Twilight: Phoenix! Language!
Gilda drops a few "Damn"s in her interrogation out of anger (which makes Twilight Death GlarePhoenixfor some reason). She also leaves out a "Crap", but given the circumstances, no one calls her out on it.
The normally unflappable Prowl has a couple of these in Things We Don't Tell Humans, one as a child, establishing his intense dislike of Sentinel Prime, and another when Terratron allows his students to gather together in public.
Considering the whole Zalbaar-being-captured-by-Gamorean-slavers circumstance, it's understandable
In Pretty Cure Hollywood Stars, Lina gets a Precision Black Strike, and because she's white it is NOT the N word (it's been stated numerous times in-story that she isn't racist, though she does drop an epiphet from time to time and gets called on it by either one of the other characters or the narrator). Here's a hint: think Clint, for whom the author named her.
In Reconciliation, this happens at two different points in a single chapter, as Lilly is undergoing an emotional breakdown after her husband Hisao's funeral.
Akira: "Help me to understand here, Lilly, because right now I’m getting really fucking scared. I’ve never seen you like-”
Lilly: “That’s bullshit. My husband is dead. He’s dead, Hanako, and he’s not coming back.”
Talking of Gurren Lagann fics, Nia also gives a Precision F-Strike in Sound Of Heaven Pulling Down, during a discussion, but she doesn't seem to be aware of the meaning of the word "fuck". Simon even lampshades it, saying he won't swear next to her anymore.
Kuushou aka Kyuubi doesn't necessarily shy away from cursing. However, one occasion that really stands out is when he learns that virtually every ninja skill (including chakra control exercises) is considered advanced training, and thus not taught until after graduation.
Kuushou: "For fuck's sake! How in Kami's name did you let those kids graduate?"
When Mai encounters Nao in the hospital, learns about her comatose mother, the incident that led to that, and that Nao had to let that incident happen to avert a temporal paradox, she offers her condolences, but Nao, embittered and thinking of most people's expressions of sympathy as being empty and insincere, shoots back with "You're fucking sorry?".
After 18 chapters of nothing worse than "damn", "hell" and "arsehole" in Warriors of the World, the character most likely to swear calls someone else a "little shit". This turns out to be an OOC Is Serious Business moment, as he only swears that severely when he's trying not to resort to violence or anger.
In Saki After Story, while there is a fair amount of profanity, Sumire's screaming "WHAT THE FUCK IS WRONG WITH YOU?" when finding Teru beating up her younger sister Saki (as well as Nodoka when she tries to help).
In Monster Movie, when Crow tries to contact Joel after Joel's caught by the shadow-thing that the SOL picked up, Joel tells Crow to "Shut the fuck up and leave me alone!" This horrifies Crow because Joel would never say that to him.