Red vs. Blue would normally not qualify for this, since cursing has almost always been one of the trademarks of the series. However, the last half of season 1 and the first half of season 2 were almost completely clean (Rooster Teeth had been trying to make the series more kid-and-work-safe). When the creators decided to reintroduce profanity into the dialogue, they did it with Caboose's "mental image" of Church, who spouted off more over-the-top vulgarity than had ever been heard on the show up to that point, a pretty major wake-up call to the audience.
Played For Drama in season 12 with Washington. The first episode he's featured in since he was captured and possibly killed starts out with his P.O.V. during the attack from the season 11 finale. He's passing out after having been shot when he sees Locus (the guy who shot him) standing above him and talking. The first words out of Wash's mouth in almost ten episodes in what he knows could be his dying breaths?
kurtjmac barely ever swears, preferring "crap" and "nuts to you" and occasionally dropping a "hell" or a "damn". In the most recent episode of the Mindcrack Ultra Hardcore series (in which well-known MinecraftLet's Players duke it out last-man-standing-style while running a difficulty-increasing mod), he goes from full health (and a very complete player-killing kit to boot) to dead, in less than a second, by glitching into a block because his (four) dogs teleported to him while his boat was near land, in memory-intensive terrain, on a laggy and crowded server. His response? "Motherfuck-" *cut to old-timey We Are Experiencing Technical Difficulties slide*
The earlier episodes of lonelygirl15 were like this. Bree swears precisely once in the entire series, in "I Probably Shouldn't Post This...", when she is defending the Hymn of One in a heated argument with Daniel: "It's my beliefs! There's a million fucking different religions in the world!"
Notably, Linkara (who never uses stronger language) actually referred to a character as a twat in his JLA: Act of God review. Also in that review, he uses the word "goddamn," which is all the more appropriate as the comic was partly written as Christian propaganda.
In one crossover review with Bennett The Sage, he had Bennett do the Precision F Strikes for him. Linkara paused when most people would curse, and Bennet said the F-word for him.
And then when he made an appearance in Bennett the Sage's Masterpiece Fanfic Theatre in which he was tied to a chair and forced to listen to his own teenage fanfiction, he WOULD have dropped an f-bomb...if Bennett hadn't conveniently gagged him.
He does say "Son of a bitch!" (his strongest swear, aside from a bad imitation of him by The Nostalgia Critic, who made him say the F word in a faked apology video) when he reaches his breaking point, much to Bennet's amazement.
Cry for Justice had him as close to dropping the f-bomb as he'll probably will ever get: "This is a freakin' joke!!!"
"Add up everything that you have ever done, and what do you have to show for it? Jack and shit. And jack left town."
Someone decided to rant on Linkara's blog about seeing another Jew Wario video. Linkara (basically the biggest Nice Guy on TGWTG) ended his response with "Fuck you. Fuck you and never come back." This happened AFTER Jew Wario commited suicide, it's no wonder why Linkara was so ticked.
During Con Bravo D20 Live 2014, Linkara slips up and says fuck while arguing with Big Mike, before correctinghimself immediately.
You know you're in deep shit when GOD swears, as The Nostalgia Critic found out the hard way when he called God benevolent when in fact he was vengeful.
God: Your ass is grass.
An OOC Is Serious Business occurs in AJCO when Egg, the quiet teenager who had sworn only once up until this point (and even then she was only mimicking Kube in a friendly fashion), swears at A_J following her removal from the hangar and the news that she will be expelled to the radioactive outside world.
<Egg> F-fine. Fine. Iíll take the bullet, or the gas, or the radiation. But at least I was liked. And loved. Unlike you, you heartless bitch.
Used spectacularly in Survival of the Fittest. Yes, while most characters swear like sailors, cute, meganekko, sugary sweet Louise "Lulu" Altaire manages to pull this off. When she meets Lenny for the third time, after he has just killed her friends the previous times, this time she's prepared. She's killed people, she has a gun and isn't afraid to use it.
Lulu: See this thing, Lenny? Now you take your fucking hands off your handgun or I'll blow a hole through your head.
(Rage builds up within the Nerd) F...F... Curse! Curse, Goddamn it! Mnh! I used up all my fuck points during the last 107 episodes. I don't have anything new. I gotta rely on the old tricks. (Begins to fight the game cartraige RPG-style) All right. Let's try the ClusterFBombs. Fuck this fucking piece of shit fucking shit fucker game! (Game attacks the Nerd) UGH! Uhh, gotta go for the Precision F-Strike. Oh, how this game lures you in with its appealing gameplay, and charming atmosphere, and then bends you over and FUCKS you to Hell!!
Extra Credits has gotten worked up over subjects before, but has always kept it's language clean. But Call of Juarez: The Cartel's completely backwards depiction of human trafficking finally warranted a "That is f*bleep*ing disgraceful".
This guy answering a prior video's question as to why God won't answer prayers.
"Seriously? I know this is innappropriate, but what the fuck."
Interestingly, he began using more intense swears ever since that.
On a similar note to the above, Captain Sparklez rarely swears in most of his videos beyond anything stronger than "god damnit", and that's generally reserved for his non-Minecraft videos. But in his appearance on React when the subject was The Farting Preacher, he found out that his theory on the subject was wrong (he had assumed the videos were a church using viral video as a promotional campaign), and commented "I am so fucking gullible". A year later, he dropped an F-bomb when going for the "Try Not to Laugh" video, vowing to "fucking ace it".
And again in "Coffee Tactics". He also throws out the no swearing rule while playing Slender, because he finds it that terrifying.
Fred Clark's Slacktivist blog has a great example in Stop Demanding That You Get Screwed, which has 20 or so paragraphs explaining calmly and patiently why healthcare reform isn't a bad thing, then emphasises it by finishing the postscript with "fuck you, you fucking moron".
YouTube microwave show "Microwave Me" fits this trope, especially with the most common variation of the opening tagline. "Hello, and welcome to Microwave Me, the show where I microwave shit so you don't have to!", but beyond that, it's rare for him to use sexual innuendo or swear words more severe than "damn", "hell", or "ass", although this trope is subverted in this case because he considered "shit" to be equivalent to the three listed above, and not up there with words like "fuck" or "cock".
SF Debris isn't afraid to swear in his reviews, but even so, he's surprising adept at dropping laser-guided F-bombs to emphasize certain situations. This is demonstrated when he inserts his own dialogue into the Star Trek: The Next Generation episode "Where Silence has Lease," where black, redshirted Ensign Haskell proves justGenre Savvy enough to realize how screwed he is.
Nagilum: Now would be a good time to learn about death by killing one of you. Riker: Oh, no! Picard: Oh, no! Troi: Oh, no! Data: Oh, no! Haskell: MOTHER FUCKER!
Rogueamp usually has a few of these in his videos, but perhaps his most famous is "SERIOUS FUCKING BUSINESS" from the Network Crime Ransomware video.
Passing Those Who Inspire Me by Matt Santoro includes one use of "pretty damn good", but no other swearing.
Zero Punctuation has notable ones, which are hard to pin down when Yahtzee says the word at least ten times per review. However, two stand out with exceptional comedic timing:
At the tail end of his review of Child of Light, Yahtzee is talking about how annoying and poorly written the rhyming couplets that make up ALL of the narration and dialogue are. He ends by angrily yelling at the game: "You can't rhyme 'ravenous' and 'delicious'! Emphasis is on the wrong syllable! You FUCK!!"
In his review for Halo Wars, when he is recounting a particularly frustrating incident that made him stop playing the game all together, his explanation of his ire is like an F-word tactical carpet bombing (during a timed rescue mission, after he had completely cleared the map of hostile forces and the squadron he was rescuing were mere feet from the home base, the timer ran out and they disappeared, supposedly dying somehow):
Yahtzee: "'We lost contact!' went a character. BULL! FUCKING! SHIT! All possible threats were dead! We didn't lose contact, I was looking at them! They were right fucking there! We were close enough to communicate by waggling our eyebrows at each other! What the fuck happens when the stupid arbitrary time limit runs out!? Do their Battle Royale collars explode!? They all lose honor and disembowel themselves!? WHAT!? And just to put the cherry on it, you know who they were? Absolutely bloody no one! Generic faceless pricks of the sort I'd vat-grown about 50 of that day alone! But we didn't make it in time, so they were gonna make me do the whole fucking mission again! As the exasperated Chinese zookeeper said to the last male panda in the world, 'Fuck that!'
Video Game High School has skirted the line in recent seasons, but in episode 5 of season 3, Calhoun vents his frustration in a particularly non-highschool friendly way at the Barnstormers.