The House Of The Dead Overkill has the character of Isaac Washington, who averages about one swear word per sentence (his first line, also the first voiced dialogue in the game, being "What's up, motherfucker?!"). The only time he doesn't use it is to someone who actually deserved it (i.e. a literal Motherfucker)
The game is placed at the top because it is the first game ever to win a Guinness World Record in video games for this trope. The final F-bomb count? 189.
Afro Samurai is a M-rated game (based on the manga/anime series of the same name, naturally) with Samuel L. Jackson as a fucking voice actor. Granted, the titular character doesn't do a lot of fucking swearing, but Ninja Ninja certainly does. The mooks like to get in on it too.
The Metal Gear series was always fairly conservative when it came to four-lettered words, with only oneutterance of the word "fuck" in the series...up until Metal Gear Rising: Revengeance, that is, where F-bombs became as plentiful as the cyborgs in the game. Steven Armstrong easily takes the cake as the most foul-mouthed character in not only the game, but the entire series!
BioShock 2 has one of the male Splicer models yell out entire salvos of Cluster F-Bombs as his Enemy Chatter, and one of the female models (the upper-class woman) is also, but not nearly as, foul-mouthed. Other random Splicers and named NPCs moderate their language noticeably well in comparison.
The swear density was so ridiculously high in this game that it made Scarface (1983) look tame in comparison. Fuck you fuck!
Company of Heroes: Opposing Fronts features much more swearing than the original game. The British say "wanker" a lot, and the Germans use such colourful expressions as "Leck mich im Arsch" (also the title of a composition by Mozart which your school music teacher probably didn't teach you) and "Hurens÷hne".
Grand Theft Auto: San Andreas was the first GTA game to make use of F-bombs, and dropped them at every available opportunity. One gaming magazine retrospective complained that it made the characters sound less like bad ass gangstas and more like twelve-year-olds out of adult earshot.
365 times, to be exact. And that's not including pedestrian dialog & radio.
The original Grand Theft Auto had a 'special' file which contained the same dialogue text, but with the profanity cranked Up to Eleven. To name a couple of examples, "Move your sorry butt before it blows!" became "Move your fuckin' ass before it blows!", and "That'll teach the bald man a lesson" became "That'll teach the baldy fuck a lesson".
Though the F-word is notably absent, both Cid and Barret from Final Fantasy VII deserve a mention, especially Cid. One of his first scenes contains the memorable line "SIT YOUR ASS IN THAT CHAIR AND DRINK YOUR GODDAMN TEA!" and his reaction to seeing the apparently M.C. Escher inspired Temple of the Ancients is, "Shit! Shit! Shit! What the hell's with this place?"
Also: "Hold on to your drawers, an' don't piss in 'em!"
Considering the game is T, and it uses profanity of varing degrees VERY liberally, it should be in a trope of its own. Most notably, it seems that Barrett drops the F-Bomb every ten minutes, and its BLEEPED OUT WITH RANDOM SYLLABLES!
A crowning moment of cursing comes from the flashback about Cid's original launch attempt into space. Right when the launch is about to happen, he leaps out a huge, uncensored "SHIIIIIIIIIT" before aborting the launch to save Shera. Definitely not a humorous moment, but it is probably the best example of the cursing the game involves.
In The Longest Journey there is a character named "The Flipper" who averages 2-3 swear words per sentence, even introducing himself as "The Fucking Flipper" at one point.
Bulletstorm is known for two things: violently creative ways to kill enemies, and an overabundance of swearing. The game designers did not speak English, so they never realized that they were using swearing as mundane speech, and the main characters using swearing as a fluent language is now a core feature of the game. This video even has them admit the language is 'colourful'. With D, T, S, C, A... all the other letter bombs to join it. The ending of that video alone has the Player Character say "Hey dicktits! This game isn't going to preorder itself!" A Fan Nickname for the game is Captain Swearword's Big Fuckin' Adventure.
Parodied in the "Meet the Demoman" trailer for Team Fortress 2, where the Demoman mutters drunkenly about his problems, and a long section is beeped out.
The multiplayer announcer in Kane and Lynch has a tendency to drop these, especially by by spamming "fucking traitor, make him pay" after every "friendly"-fire kill, which happen often in the game.
Not to mention the single player game.
Kane: Shit! Fuck! That old fucker took it.
Lynch will also begin screaming random curses during his psychotic breakdowns. Of course, he always talks like that anyway.
Both Max Payne games feature a mob boss named Vinnie Gognitti. His life seems to be powered by this trope.
The first game is largely non-profane, with the biggest offenses being the word 'Bullshit' once by Max, and screwing, quite frequently, by Vinnie. In the sequel, Vinni is a regular Joe Pesci.
The game Metal Arms: Glitch in the System has a character named Krunk, a robot who looks like a potbellied war vet, and because all the characters are robots, has a censor bleep. For example, "Of course I f*** ing fixed him. It was a huge pain in the f*** ing wastepan, 'cuz he's some kind of custom jobbie!" He's also playable for one level, and curses whenever you're shot or if you die.
In Scarface: The World is Yours, Tony fucking Montana comes close to the usage in the film once he enters blind rage. Also, if you die, the game tells you, "You fucked up". And when your wanted meter fills up? "You're fucked."
In No More Heroes, the first fucking words spoken by the main fucking character Travis Touchdown are a rousing shout of "Fuckheads!" as he decapitates several guards. You can more of the same during the rest of the game.
"That's fucked up! That's the stupidest rule I've ever heard! This guy's mine, and you want me to just let him go? Bitch?! Whatever, but this dude says he wants to fight, and ain't nothing gonna stop him. This ass clown right here is— Hey! He's gone! Mister Sir Henry Motherfucker, he just jetted! What a pussy!" (said right after Henry kills Letz Shake before Travis gets his shot)
"This isn't a battle anymore it's a mother fucking war!"
The Black Baron (stop starin') is all about this. His memorable pre-Bloodbath Challenge tirades almost always use "fuck" and other such swears. An example, for Money Shot II:
The Black Baron: And the Black Motherfucking Baron is gonna be a pimp to teach yo' ass! The rules are simpler than turning out an ugly, broke-ass college girl from Kansas: just pop corks in some marks and send 'em flyin' sky high. Except the bitches you gonna be poppin' corks in ain't gonna mind, 'cause they alien asses used to be space cadets, y'know wha' I mean? ...baby, baby, you wanna money shot yourself, don'cha? Ha, ha...all right, folks, she don't talk too much, but she is just some freaky shit, lemme tell ya. She could take a pop! ...baby, tell 'em who lays the muthafuckin' money down! (bottle being rammed down his throat) Aw, HELL naw! (SPLUT)
Colonel Vanek, a major villain from FEAR 2 is prone to this. In fact, his last words are basically a long string of swears.
Lt. Stokes also doesn't give a fuck what people think about her language.
In the visual novel Kira Kira, one scene features the main characters 'learning how to swear', as they're trying to become punk rockers and punk rockers swear a lot.
Naturally, this leads to hilarious situations with improper use of the word, made even funnier by the awkward Japanese pronunciation:
(While working in a restaurant:) Maejima: "Yo, have you decided what the fuck you're going to order?" Kirari (smiling innocently): "So this mother fucker customer wants a fuckin' beer, right?" Manager: "What are you saying?" Maejima and Kirari: "Nothing! Fuck off!"
Maejima was told not to come back to work for a month after this scene.
The Witcher is quite generous with its swearing. But then there's also Thaler, who starts dropping cluster F-bombs as soon as he opens his mouth.
In the sequel, a prisoner delivers a truly epic Cluster F-Bomb that loses something in translation, but approximates to "You son of a bitch! Fucking prick! Fuck you, fucker! Fuck you up the arse! Fucking motherfucker, fuck you, you hear?"note "Ty kurwi synu! Chuju jebany! Pierdol się, pojebie! Chuj ci w rzyć! Matkojebco chędożony, zajebe cię, słyszysz?"
In Mass Effect 2, when you take control of Joker while the Normandy is overrun with Collectors, half his dialogue during the sequence is repetitions of "shit!" And given what's going on, who can blame him?
In the same game, party member Jack is known for her potty-mouth. In ''Mass Effect 3, Jack is a teacher if she survives the events of 2, and makes an effort to watch her language around the kids. Joker teases that her swear jar could fund the war effort by itself.
At which point, Jack tells her students to cover their ears and lets loose with months of saved-up swears at him... presumably. The scene cuts away at that moment.
In one very memorable sequence in Red Dead Redemption, main character John Marston joins in on a poker game between Landon Ricketts, a couple of Mexicans and a German. When a few hands go Marston's way, the German, Muller, falsely accuses Marston of looking at his cards and is none too happy:
Muller: You fucking cheat! You fucking looked at my fucking cards, you fucking cheat! There is no mistake, your Yankee friend here is a fucking cheat.
The protagonist of Silent Hill Home Coming, Alex Shephard, swears a lot more than others when he faces some disgusting monsters.
Mafia II has been given a Guinness world record for the most uses of 'fuck' in a video game. The amount? Well, they stopped counting at 200, but they requested a game script for a final tally.
KainÚ from NieR has a particularly foul mouth, as often commented on by the other characters. One particularly memorable rant is replayed in the introductory sequence every time you turn the game on.
Weiss, you dumbass! Start making sense, you rotten book, or you're gonna be sorry! Maybe I'll rip your pages out one-by-one, or maybe I'll put you in the Goddamn furnace! How can someone with such a big, smart brain get hypnotized like a little bitch, huh?! Oh, Shadowlord! I love you, Shadowlord! Come over here and give Weiss a big sloppy kiss, Shadowlord! Now pull your head out of your Goddamn ass and START FUCKING HELPING US!
Dana Mercer in Prototype does this a lot, even before the player first meets her: her very first line is "Let go of me, you goose-stepping motherfucker!" The Blackwatch soldier capturing her — and Blackwatch are hardly the most delicate speakers in the game — is downright shocked.
In the sequel, many characters swear. But the player character, James Heller, is the most foul-mouthed of all of them. Lampshaded by Alex Mercer
In the Aksys Games English translation of Hakuōki, Hijikata Toshizo's rude and confrontational manner of speech is conveyed by liberal use of profanity, including a couple of heavily F-bomb-laced rants when he hits the Rage Breaking Point.
There's a reason Jet Set Radio Future got a Teen rating for "Strong Lyrics". Listen to Rockin' the Mic and you'll see why.
PAYDAY: The Heist has a ton of F bombs being dropped during the assault waves from the cops, ranging from "OH SHIT! IT'S A MOTHERFUCKING BULLDOZER!" to "Stay the FUCK down! And don't you FUCKING move!"
The first boss of DmC: Devil May Cry, Poison, is introduced this way, seemingly adding in a curse every other word.
Poison: You want to kill me? You can't kill me! I'm twelve hundred years old!
In Conkers Bad Fur Day, "fuck" is the only word that is censored. All others are said loud without problems.
In the Loyalty story of BlazBlue: Continuum Shift, Hazama drops a cluster S-bomb when Hakumen evacuates a paralyzed Tager from right in front of him.
Shit! Shit shit SHIT! Hakumen, you are a real thorn in my side...! Ugh. Whatever. I've got more important work to do.
From Borderlands 2 there's MISTER. TORGUE. Luckily, his company's shareholders realized the fallout of Mister Torgue's constant swearadio advertisements, so they installed a voicebox implant that bleeps out every basic swearword. Unfortunately for said shareholders, the implant does not give Mister Torgue a punishing electrical shock to slow the swearing, nor does it deal with religious swearing. It's hilarious.
In the Japanese dubs of Magical Drop II, III, and V, Chariot is prone to shouting "KUSO!" (which roughly translates to "damn" or "shit") whenever his opponent attacks him. In the hands of a bad player or AI, Chariot becomes quite the pottymouth.
Mondo Owada of Dangan Ronpa is so prone to saying this a lot, even more so when it's not fully-voiced dialogue. Other characters only say this when they start to get very pressured about current events.