Undoubtedly part of the reason for the success of Sylvester Stallone and Arnold Schwarzenegger in their heyday - just like Steve Reeves, Reg Park and the other bodybuilders turned stars of Hercules and other Italian sword and sandal flicks who inspired them. And continues with their successors Vin Diesel and Dwayne "The Rock" Johnson.
The late Burt Lancaster, a former circus acrobat before he took up acting, was one of Hollywood's earliest examples.
Think the Andy Sidaris collection is all about BBB, or Bullets, Bombs, and Babes/Boobs? His films also have no shortage of buff men (including a man called Buff) walking around shirtless, or with open shirts, vests, or jackets.
Rob Lowe's nude scenes in Youngblood, About Last Night and Masquerade.
It's difficult to find a film in which Jason Statham appears and doesn't take his shirt off at some point. The Transporter includes three (count 'em, three!) shirtless scenes.
Jean-Claude Van Damme, full stop. He must have a contract stipulation that states he must show his bare ass at least once in every movie he's in, and he spends a good amount of combined time shirtless.
In Beyond the Lights, Kaz (Nate Parker) spends an awful lot of time sans shirt. On one occasion he ups the swoon factor even further by removing the garment (which just so happens to be WHITE!) specifically to use as a towel to clean the blood off Noni's hand after she injures it by smashing posters of herself during a breakdown. AWWWW!
In the first film, both (trim and muscular) McManus brothers are seen shirtless when they awaken from the vision/dream.
In the second film, Connor and Murphy get an outdoor shower scene.
Casino Royale (2006) is just chock full of naked, shirtless and tiny-swimsuit-wearing Daniel Craig. The scene to the right was pure dumb luck due to where they were shooting (the water was too shallow so Craig couldn't swim and had to stand up). The director decided to Throw It In! and Craig proved he could live up to Bond's Mr. Fanservice status.
Vincent Perez in Indochine spends most of his screen time staring vaguely past the camera with his open shirt flapping around his impressive pecs.
The film Into the Wild. Emile Hirsch spends a significant part of the film in a state of close up shirtlessness.
I, Robot starts with Will Smith's character in the shower.
Thor from the 2010 film Kaboom is nothing but a Mr. Fanservice.
Paul Bettany as Geoffrey Chaucer in A Knight's Tale. Spends his entire very memorable introduction sequence (several minutes long) completely naked and in desperate need of a scrubbing. He's naked again not long after that.
Trent, the male protagonist of Lawn Dogs, has several shirtless scenes, wears shirts with varying numbers of buttons undone, and has a full nude scene near the beginning of the film for good measure. Not to mention all the sweat he works up.
Magic Mike is a film about male strippers. The Powers that Be were aware of this, as one of the bonus features of the DVD was all of the stripping scenes strung together without any of that pesky dialogue or plot getting in the way.
In Maleficent, Diaval is naked when he is first turned from raven to human. He later wears rather loose shirts that are open — allegedly the intended effect was to make him look like a pirate, but he does show a lot of bare skin, too.
In Captain America: The First Avenger — including in-universe: When he first comes out of the chamber that buffs him up, Agent Carter can't resist reaching out and touching his newly-incredible bare chest◊ for a moment. Also meta since her actress was overcome by the moment and they got some Enforced Method Acting for nothing. There's also a nurse in the background who holds out a shirt for Steve, gets a second look at him, then puts the shirt away. She is a true American hero.
Having Chris Hemsworth walk on-camera without his shirt in Thor didn't accomplish anything except for one of the characters to note he's pretty ripped for a hobo. His shirtless scene in Thor: The Dark World is just as gratuitous, probably much more so. Even Chris Hemsworth asked why it was included. He gets yet another shirtless scene during Age of Ultron, making the first Avengers the only film Thor's been in, for more than a cameo, that didn't show his body (too much). Hemsworth continues his shirtless streak in Thor: Ragnarok as well.
In The Mummy and The Mummy Returns, Oded Fehr's character Ardeth Bey acts as fanservice with fighting scenes and an accent. To some extent most of the male cast, including Imhotep... once he is less corpse and all man.
Teddy from Neighbors, natch, when you're played by Zac Efron, you're automatically this. It also helps him get a post-college career at Abercrombie & Fitch, and there's a prolonged Shirtless Scene at the end that seems to say "Thanks for watching, ladies, and now: here's the reason you bought a ticket."
The Outsiders is FULL of this. It has a bunch of guys who are usually wearing tight shirts or even no shirts. There's even a scene where Rob Lowe comes out of the shower wearing only a towel. Later, he's laying on the couch with his knees up so it looks like he's naked.
While his appearance is not clarified, it seems that if you are looking for an actor to play Romeo from Romeo and Juliet, one of the golden rules is that the actor must be attractive.
In the 1968 adaptation, he is played by a very young and handsome Leonard Whiting, also ditto for the 1996 version, with Leonardo DiCaprio. Others include Douglas Booth, Leslie Howard, Orlando Bloom and Laurence Harvey (the latter three were not very young when they played the part, but that doesn't mean they weren't easy on the eyes, either).
Garrett Dillahunt (Hogan) in The Scribbler, In-Universe. Not only does he have many shirtless scenes, but as the only guy in an otherwise all-female psychiatric halfway house, he's more than happy to sexually service his fellow inmates.
She-Devil features A. Martinez as a surly and shirtless manservant.
Shoot 'em Up: Clive Owen naked having sex and shooting things.
In The Show, Robin (John Gilbert) is definitely this In-Universe, as much of Robin's stage act consists of him and the ladies in the audience exchanging winks and lascivious glances. At the end, after one woman in the audience remarks that Salome the actress hid him in her apartment for weeks (he was a murder suspect), another woman says "Why not?"
Steven Strait, a.k.a. Warren Peace in Sky High (2005), as admitted by the director.
Terminator Salvation. Not only can Marcus not keep his shirt on, but Ahnold shows up as the T-800 at the climax. Naked.
Velvet Goldmine features young Ewan McGregor, young Christian Bale and young Jonathan Rhys Meyers. Shirtlessness, full nudity (Ewan, of course), and man-on-man makeout sessions abound.
In The Wedding Date, Dermont Mulroney as Nick Mercer, a male escort who hired by Kat Ellis (Debra Messing) to pose as her boyfriend. He has no problem about taking a shower in front of her.
Chris Evans basically spent much of What's Your Number? naked or at least in various states of undress.