"I'm too sexy for my shirt, Too sexy for my shirt, So sexy, it hurts!"
— Right Said Fred, "I'm Too Sexy"
The most common form of fanservice for anyone attracted to men. A hunky man (real or animated) goes shirtless or wears a revealing top that shows off his pectorals. Saves the crew a fortune in wardrobe (or ink) for Mr. Fanservice.
A less fleshy version of this would be his wearing a t-shirt pulled back over the back of his head or his leaving the shirt totally unbuttoned. Also a practice of slender bishonen in Japanese media, especially Yaoi Guys. Western shows may play around with this by having the female characters ogle the "pool boy".
Despite applying mostly to young, hairless types such as Bishonens, some men will occasionally sport a Carpet of Virility. Of course, their pantswill always stay on. (Well, almost always...)
"Beefcake" poses for male performers probably date as far back in human history as skimpy outfits for female performers. One of the standard props of certain kinds of "Strongman" performers in circuses and such is a "tear-away" shirt that can be pulled off during a performance and then easily sewn back together in between shows.
This type of gratuitous semi-nudity is also called a Shirtless Jackman Scene, named after muscular Australian actor Hugh Jackman whose film contracts allegedly contain a clause that demands the presence of at least one shirtless scene, even when the plot does not require it. It's not proven, but the majority of the films he has appeared in are strong evidence. Legend has it that some people are not able to recognize him with his shirt on, and X-Men (2000) established him as the pioneer of the current generation of topless male actors.
This trope is among the Always Male tropes because... well, you know. The closest female equivalent would usually be a Lingerie Scene or a Swimsuit Scene.
See also Shower of Angst, Slipknot Ponytail, Man in a Kilt, Wet Sari Scene, Forging Scene, Shirtless Captives, After Action Patch Up, and Lingerie Scene. If the character's everyday attire is conspicuously lacking a shirt, he would be a Walking Shirtless Scene.
The Sandman's title character, goth pretty-boy Morpheus, frequently went shirtless. Indeed, one of his most frequently seen items of clothing is an ankle length robe that nevertheless exposes his skinny but toned midsection, allowing him to present the image of the authoritative King of Dreams while still providing the expected fanservice. And people think Sandman's biggest selling point was its sophistication.
Not to mention that he's buck-naked in his first appearance.
The actual number of times this has happened to various superheroes is too many to list, especially including characters with nothing but shirtless scenes (Namor, Hulk, etc.). It's safe to say that every male hero and villain has had one of these. Except the Blob, of course.
This website covers a lot of instances in which Superheroes are uncovered from the viewpoint of someone into men. Remember that around half the world is attracted to men.
Among others, ElfQuest's main protagonist Cutter's everyday outfit does not include a shirt.
Bruce Banner in every adaptation of The Hulk always has his clothes conveniently ripped away when he transforms, meaning that when he turns back into Bruce we get lovely scenes of him wearing nothing except for a pair of baggy purple shorts which he has to hold up to stop them falling down. Of course, his trousers never tear off completely.
Well, sometimes they do, especially in the Ultimate universe.
Michael Turner apparently received constant requests to show Ian Nottingham with his shirt off.
Neal Adams would draw Bruce Wayne shirtless in the cave, although he usually had a lot of bandages covering him. Additionally, Adams popularized the "pants and mask without a shirt, cape or belt" look.
Neal Adams was also the first person to draw Batman villain Ra's Al Ghul, who is a Walking Shirtless Scene half the time. Naturally, the first Batman and Ra's fought, they were both shirtless.
The comic adaption of Storm Front has one scene where Harry, who just got out of the shower, has to fight a demon. He didn't have much time to get his clothes on. Not that anyone's complaining; especially his kind-of girlfriend, who just drank a love potion on accident and is trying to have sex with him.
2007 World Men's Champion in figure skating Brian Joubert has a tendency to wander around shirtless backstage at competitions, and ESPN has a tendency to include a clip of it in their broadcasts of every competition he's in. These days they even lampshade this piece of fanservice turned Running Gag, with comments such as "And there's your obligatory shot of Brian Joubert shirtless," or montages like this one. He may claim that he takes the top of his costume off just because he likes to, not because he wants to show it to everyone, but when you consider he's deliberately posed shirtless for magazine photos and the state of even further déshabillé he's appeared in on TV in his native France, one must wonder...
Boxing of every sort.
Wrestling of every variety. At least they wear more clothes now than they used to! Of course, women weren't involved in that kind of thing. That would just be obscene!
The Ultimate Fighting Championship has violence for the straight guys and beefcake for everyone else. Just like the good old days of Ancient Greece and The Roman Empire! They don't sell Ultimate Fighter sweat as an aphrodisiac, though...yet.
The Beautiful Game sometimes has the customary jersey switch after the game, as well as celebrating goals by pulling one shirt over the head from the front (though the rules forbid that in big games). And of course, at the end of the game, players are sweaty and tired, so the shirt comes off pretty easy. Which infamously leaked over into the women's game in 1999, on the biggest stage. Yes, straight males can occasionally get something out of this trope.
The beach and water versions of most sports, such as volleyball, wrestling, polo, and the like.
The practice of Shirts vs. Skins is still around, though not quite as common as in the past. Shirts vs. Skins is a method of distinguishing between two teams in a game. One team takes off their shirts, and is therefore called the skins, while the other team keeps their shirts on.
In 2003 England's rugby team introduced new skin-tight strips - but early on when the design hadn't been perfected yet, every match saw at least one sweaty muscle-bound rugby man with his shirt hanging off him in true Shatnerian fashion. It was fantastic.
The all male Davinci Body Series workout videos have each of the participants including the instructor performing in the nude.
Cassius from Julius Caesar, ecstatic about the conspiracy to kill Caesar, bares his chest to a thunderstorm one night and, according to the script, appears with his shirt unbuttoned. As the manipulative Cassius could easily be considered the villain- and is also described as being quite lean- this can cause some happiness among female Shakespeare geeks.
Chris in Miss Saigon has two. He's post-coital in one scene and pre-coital in the other, so it's not as gratuitous as most examples.
Terrible Advice, a black comedy play by Saul Ruibinek of 'Warehouse 13' fame, featured a certain Scott Bakula in nothing but board shorts for the first 15 minutes. Ummm.
Arthur Miller's play "All My Sons" has Chris shirtless at the start of the second act.
Daichi greets Sasha and Iphigenie wearing nothing but a towel in Greek Ninja.
Broken Saints. Big time. Oran spends half the series shirtless, Kamimura and Raimi join him in shirtlessness for Chapter 20. Gabriel goes completely nude early on and later on goes shirtless for the Grand Finale.
Jonas in lonelygirl15 is very often shown without his shirt. This aspect of his character is eventually lampshaded during Sarah's rant in the season 3 episode "Adios Amigos".
Parodied by College Humor in their Call Me Maybe Parody. Like the music video, an attractive guy starts lawnmowering a backyard, but when a girl takes note of him and he takes his shirt off, he's revealed to be a Neo-Nazi on account of the huge swastika tattoo on his chest.
The Autobiography of Jane Eyre: Downplayed in episode 11. Mr Rochester has loosened his shirt and a tie, and he has rolled up his sleeves, revealing his geeky tattoo. Fangirls approve.