This trope became very common in comic books in the 1980s; previously, death in comic books had been very rare, but with the loosening of the Comics Code in the mid-70s, it happened more and more often, to the point where it's nearly a Discredited Trope now (as is Back from the Dead).
Next issue: Not a hoax! Not a dream! Not an imaginary story!! The story they didn't think we had nerve enough to tell! Thor croaks!!!(It's the beginning of the notorious "Frog Thor" storyline.)
Parodied, along with other comic book death tropes, in the Marvel GLA (Great Lakes Avengers) limited series. The series promised not one, but two characters would die each issue. However, one would be Mr. Immortal, who has Contractual Immortality as his power. As there were only four other members of the GLA, and issue one did kill member Dinah Soar off for real, the GLA would be more or less nonexistent by the end of the series. However, the team goes recruiting, and the next deaths would include Grasshopper, who was a member of the team for 5.8 seconds (in a parody of Marvel's penchant to give a complex background to a character only to kill him off to show Anyone Can Die), and Monkey Joe, new member Squirrel Girl's pet squirrel - whom she had spent the issue trying to convince the GLA to accept as a genuine member (just when they did, guess what happened). The final issue saw original member Doorman die, but he was Back from the Dead before the end of the issue.
Avengers: The Initiative #10 featured the Initiative's most significant cadets on the cover — and also promised one of them would die on the inside. It was one of the Scarlet Spiders.
In issue #19, it is revealed that the newest person to don the Grasshopper suit is a Skrull. He is subsequently killed by the aptly named Skrull Kill Krew It might as well have "Tonight, The New Guy In The Grasshopper Suit Dies!" on the cover.
Runaways did this twice: first for Gert's death, and then in the last arc before going on hiatus ( Old Lace). The second time amped it up with "One will die...one will live again."
Parodied on the cover of the Doom Patrol Doom Force special, where the "WHICH ONE OF THESE HEROES WILL DIE?!" cover blurb is inside a huge arrow pointing at Shasta the Living Mountain.
In the 100th Twisted Toyfare Theatre strip, the cover page boldly proclaims that "TONIGHT, ONE OF THESE CHARACTERS WILL DIE!", prompting Mego Spidey to say "Hope it's me." Ironically, Spider-Man was the only character on the cover who didn't die.
In Teen Titans (vol. 3) #74, a casket was pictured on the cover, which read, "Another Titan dies!" Although it was a poor call on DC's part to highlight how many Titans have been killed over the past few years, Eddie Bloomberg (who was depowered anyways) did bite the dust.
X-Force/X-Statix was a genuine Everyone Will DieAnyone Can Die canon, but they played this trope moderately straight in the run-up to Edie's death. The story features various highly contrived scenarios that spoof this trope, but the drama is completely genuine and the death is real and permanent. The three main members of the team each have an identical premonition that one of them is going to die. Throughout the arc, events continue to make it look like one character or another will be the one to be killed...until it climaxes with the three of them stuck in a doomed spaceship, with only room in the escape pod for two. They play dice to decide who has to stay behind. The story uses the simple title "Someone Dies."
A mid-90's Green Lantern issue once featured three important characters on its cover, with the headline "WHO WILL DIE?" The person killed was...a minor character who wasn't on the cover, showed up out of nowhere, and was brought back from obscurity just so she could be killed off.
The editor lampshaded this in the letter column, admitting that the cover had been a bit of a bait-and-switch (but also pointing out that technically, they didn't say anyone on the cover would die...)
The third issue of X-Men 2099 prominently featured this hook on the cover. However, a Genre Savvy reader could fairly easily guess that it was going to be Serpentina. Most members of the team were more developed than her, and her character was a perfect candidate for being Stuffed In A Fridge.
Inverted in the old Batgirl series, which had one cover promise that nobody would die in that issue. Someone dies.
The point of the issue was that Batgirl had personal reasons for seeing to it that nobody died on that night (It was the anniversary of the day she killed a man as a little girl). The man who was executed technically died the next day.
The X-Men crossover Second Coming promised the death of a major character. However, a combination of foreshadowing and some very obviously shifting Character Focus in the early chapters telegraphed well in advance that the person to die would be Nightcrawler.
The "This Issue: Batman Dies!!!" (three exclamation points mandatory) "cross-under" of February 2001 takes this trope and runs with it. All of the February 2001 issues of DC's Bat-Books featured the stamp, and all featured Batman dying... kinda.
In Robin 85, The Joker, bored out of his mind during his imprisonment at the Slab, has a hilarious heart-to-heart with his therapist concerning how he views Robin. During said interview, the Joker acknowledges that there have been multiple Robins, and theorizes that there may have very well been multiple Batmen throughout his career as well, meaning that at certain points, he might have actually killed Batman once... or twice... or thrice. Cue a page of little doodles showing Joker killing Batman with various deathtraps, all of which take place strictly in his head.
In Detective Comics #753, Two-Face creates a comic book as part of a new therapy program. Said comic book features Harvey Dent ("Copernicus Dent") as a Marty Stu action hero, pit against Two-Face ("Janus") the diabolical criminal mastermind. Janus has an army of Batmen as his henchmen, which Copernicus slaughters by the dozens throughout the course of the comic.
In late 2010, a Fantastic Four storyline (called "Three") began, which Marvel promised would feature the death of a team member.
In January 2011 the storyline ended with the death of The Human Torch.
They followed this up by promising that, due to the popularity of this event, they would start killing a main character every quarter, adding "This is not a joke". The sheer amount of Death Is Cheap this is expected to result in led to the move being widely mocked.
Used on the splash page of Locke & Key: Keys To the Kingdom #4. "Keep your hankies handy, true believers... because in this issue... SOMEONE DIES" And at the end of the issue, an action figure is brutally slaughtered. In this case, the action figure might actually be a character, it's not clear yet.
Spoofed in X-Factor #229. The cover features the statement, "In this issue, one of these characters will DIE!" All of the characters on the cover are copies of Multiple Man... whose Me's a Crowd power means he's in the top five most killed characters in comics.
Similarly, the cover of X-Men Unlimited Vol 2 #9 declares "This issue: Wolverinedies!" with Wolvie being blasted by a Sentinel. The story is a character piece about Logan reflecting on how often he's reached the point of death, only for his Healing Factor to bring him back.
The cover of Captain America 319 showed Cap surrounded by silhouettes of eighteen minor Marvel villains and proclaimed "If Cap can't stop Scourge, every super-villain on this cover will DIE!!" He didn't, and they did.