Alias, by Brian Michael Bendis was the first series of Marvel's mature readers MAX imprint, and indeed was part of why the imprint was formed. The word Fuck is the very first of the series, in the first panel, and is repeated twice again on page 1. The rest of the series is absolutely rife with swearing, but the early introduction of the word is quite effective.
During the "Fernus" JusticeLeague storyline. At its climax, Fernus, aka the Superpowered Evil Side Martian Manhunter never knew he had, uses his vast Psychic Powers to launch nukes all over the world. While the League desperately tries to prevent a nuclear cataclysm, Fernus makes the following observation (not exact words):
They've managed to stop a few of the missiles. But there are many more left. And Superman has just uttered his first real swear word in years. That has to count for something.
During the Funny Animal miniseries, Captain Carrot and the Final Ark!, superheroic turtle Fastback uses a lot of Gosh Dang It to Heck! type expletives. When fellow superhero Pig Iron asks him what exactly "shoot a mile" means, Fastback is interrupted during an explanation of expletives by an appearance of the villain Frogzilla, causing him to shout out a (censored) example.
In the SLG comics continuation of Gargoyles, the normally sweet and polite Angela lets out a "YOU BASTARD!" When she sees Thailog standing over her father's limp body while brandishing a bloody blade. Underscored by the fact that she just happens to be dressed like Dorothy Gale from The Wizard of Oz at the time.
In Preacher, the Anti-Villain Hoover has been struggling with being a bluenose who can't bring himself to drop the f-bomb. When Starr kills Featherstone, he finally musters the rage to say the word.
Earlier in the series, a rather meek man (described as "the unluckiest cop in the world") is partnered with a BadassCowboy Cop. On discovering that his partner is a homosexual masochist, he undergoes "the first time in my life I ever swore":
Are you sure you're not just fucked in the head?
Used in Cerebus the Aardvark. Jaka rejecting Cerebus in favor of her husband causes him to utter the word "shit" for the first time in the comic's run.
Powerpuff Girls #16 had a story with the demonic figure Him in a story with the malapropism title "Hell Toupee."
Bone is chemically free of swear words... with one exception. When discovering Phoney Bone's "Dragonslayer" bluff, Lucius Down asks him "What the hell do you think you're doing?" Made all the more notable in that he's uncharacteristically calm during the entire scene.
Castle Waiting is very sparse with the swear words, though some characters occasionally make use of a bit of Symbol Swearing. There are, however, a couple of uncensored "Damn"s, the most noticeable coming from Lady Jain after a Freudian Slip has caused her to blow her secret.
Oddly enough, with all of the taboos Sin City deals with, swear words are usually PG-13 rated and sparse. There has only been one F-bomb in the entire series: "Make a missing person's case out of this fucker!" when The Colonel is killed.
Played for laughs in an issue of Valiant's Super Mario Bros. series. No, really. Princess Toadstool finds herself on a magic carpet, rising higher, and higher. Her reaction? "Oh, %#@*!!!" And then she does it again upon being discovered by some Pidgits.
In Lucifer, the angel Duma manages to achieve all that a Precision F-Strike could hope for - a chilling dawning realization that the entire world has changed and it's never going to go back to the way it was - by saying the word No. It helps that he's at least ten thousand million years old and has never spoken before.
In the new run of Young Avengers, Miss America Chavez clamps Loki's mouth shut in order to prevent him from reciting an escape spell. Then her two moms show up and start reprimanding her. So America releases her hand from Loki's mouth with a "%!@# that", allowing Loki to teleport them away.
Given that they have two underage girls in their roster, the older Runaways try to avoid using bad language. But when Xavin's mentor Chrell nearly killed the whole team AND called her betrothed Karolina a "Majesdanian tramp", said Majesdanian tramp unleashed a powerful volley of cosmic energy... and apparently some wicked swearing. As Molly Hayes remarked, "I didn't know 'Lina KNEW words like that!"
Also, an earlier story arc saw the Runaways get stranded in 1907. After the team barely escaped from a vicious gang war and an attempted bombing, Molly swore for perhaps the first time, declaring that "Nineteen-oh-seven is ASS."
In the origin of Blue Lantern Saint Walker, he appears first as the incredibly serene, religious and hopeful man readers are already familiar with, climbing up to the peak of a sacred mountain with his family. They're trying to find their dying world's messiah, but one by one Walker's loving family dies. When Walker reaches the mountain top and finds no messiah, he yells at his God, with possibly his first profanity and blasphemy ever.