The film Into The Wild. Emile Hirsch spends a significant part of the film in a state of close up shirtlessness.
Pick a movie with Mark Wahlberg in it. Any movie. Chances are he takes his shirt off.
Chris Evans in Fantastic Four... when his powers flared up while skiing and somehow turned a snowbank into a jacuzzi, would any straight woman or gay man have turned down that invite? And watching him awkwardly prance around naked afterwards...
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.
Terminator: Salvation. Not only can Marcus not keep his shirt on, but Ahnold shows up as the T-800 at the climax. Naked.
Stephen Lang as Colonel Miles Quaritch in Avatar. Spends half of the movie in tank tops that show off his brawny physique. For a 60-year-old man, he looks damn good.
Shoot 'Em Up: Clive Owen naked having sex and shooting things.
The Boondock Saints has the two McManus brothers who have several shirtless scenes.
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.
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.
The eponymous God of Thunder (played by Chris Hemsworth) in the 2011 Marvel Universe film Thor, complete with extended shirtless scene. As Darcy says, "For a homeless guy, he's pretty cut."
