Dark Nights: Death Metal: During Robin King (Bruce Wayne) solo tie-in his internal monologue mentions a feeling of being watched and he implores whoever's watching to learn from his example and cheer him on. In another tie in, Scary Stories to Tell in the Dark Multiverse, he speaks with the reader directly.
DC Infinite Frontier: Psycho Pirate spent some time as a figure people sought out for power, but he rejected because none of them realized that their reality was only recently created from a Crisis reboot. To demonstrate his displeasure he rips the panel apart to drop them both into the Blank White Void of the panel gutters.
While the Joker is occasionally like this in normal comics as well, in the Emperor Joker storyline, where he gains 99% of Mr. Mxyzptlk's powers, he becomes one of these big time, occasionally making references to the comic and the industry, which the other characters usually ignore. Among the best of these that he did was sticking a "Why Didn't Anyone Call In To Save Me" sign on Jason Todd's skeleton (a reference to the fact that DC used a phone-in poll to decide whether he would live or die), and, faced with the fact that he couldn't erase Batman from existence due to his obsessions, yelling at the artist to stop redrawing him.
"I wanted you all to have a little more fun. And to sell a whole bunch of issues." [offpanel Superman] "What?" "Nothing."
Gene Luen Yang's run on Batman/Superman includes a story (#22, 2021) in which Mr. Mxyzptlk temporarily bestows his fourth-wall breaking powers on Batman's adversary Calendar Man, figuring he will appreciate the knowledge that reality is organised in a series of little boxes. Calendar Man learns Batman's secret identity by looking into another panel that shows Bruce in the Batcave with his cowl down, but can't get anyone to believe him.
As is Animal Man. His entire series played with the Fourth Wall constantly. Later on, he temporarily ascended to a higher plane of existence which upgraded his powers and also caused him to learn all of his life was a comic book. He temporarily suffered a Heroic BSoD until he was able to use it to his advantage. He begged the author of the comic for his family to be brought back to life after the author supposedly killed them all to make him Darker and Edgier. The author was leaving the book anyways, so he agreed. When Animal Man called the author out on his Writer on Board agenda towards showing the evils of eating meat, the author admitted it, but then quickly threw together a bunch of crappy supervillains to fight Animal Man to teach him a lesson while he both apologized for it and then ranted about how Humans Are Bastards so eating meat is wrong. Since then, he's learned to live with it, although he still comments on it from time to time. For instance, when he's asked for help from other superheroes, he usually says something like "Oh God, I hope it's not another crossover where they kill off a bunch of C-List heroes like me."
JLA (1997): There was an issue where Martian Manhunter sought Animal Man's help on something. Animal Man replied by breaking into hysterical sobbing and screaming "Oh god no I'm integral to the plot!". Manhunter left a bit creeped out by A.M.'s "unique" view of the universe. His New 52 incarnatioin lost the fourth-wall-breaking.
In the pre-New 52 Harley Quinn comic solo, usually an imaginary Harley comments to viewers on events in the comic.
The Multiversity: Captain Allen Adam from Earth 4 addresses the readers and acknowledges he's in a comic book.
