DickGrayson. There's a reason why he always ends up parading around shirtless or in his underwear, and his tendency to get tied up... often while shirtless or in his underwear. It's because Nightwing makes female Bat-fans.
All the male Robins. You've got Jason, who has a dark and troubled past and a tendancy to wear leather jackets. Tim, the king of Adorkable. Even Damian has his fangirls.
Witchblade has Ian Nottingham. Often drawn shirtless due to fannish demand. (Not that Kenneth Irons was half bad, but he spent less time half naked.) And we shouldn't forget The Darkness' Jackie Estacado, either... although he does have a slight impediment for estrogen fun.
Gambit of the X-Men is this (especially in the '90s): The dark, brooding and mysterious guy with a horrible past and a dark secret, a cool gimmick, a trenchcoat... and the playful nature of playing basketball shirtless. Or showing his magnificent butt to the 'camera' (i.e. boathouse scene or the arrival in the Onslaught-aftermath issue of Uncanny X-men).
Before Gambit, Longshot played similar role, both in his own mini-series and as a member of the X-Men. The main differences are that he didn't have a longcoat (though his leather clothes certainly were meant to invoke '80s cool, just like Gambit's clothes invoked '90s cool), and instead of being a brooding yet loveable rogue he was a naive (due to being an amnesiac alien from another dimension) yet loveable rogue. He was also co-created by a female writer.
Savant, from Birds of Prey, was designed to be a hot one shot villain but became popular.
Empowered's boyfriend ThugBoy. Lessee... Half German/Italian, half Japanese (for the all-important manga eyes and long, silky black hair), blessed in the lunchbox, really buff, more likely to be shirtless than not, more likely to be trouserless than not, more of a dark and troubled past than a third of the other examples, a prime example of Love Redeems... and loves his Cool Shades.
Inevitably done with Steelgrip Starkey, given that he spends almost all his time wearing a red short-sleeved shirt that shows off his muscled arms and washboard abs. Justified in that one reason he was selected was because he matched the archetype of a hard-working American hero.
Astérix The Gaul gives us Tragicomix, who is blonde, handsome, and never wears a shirt so as to allow viewers to see his very nicely built chest.
Booster Gold was made for this trope. Tall, blonde, muscular, pretty, form-fitting outfit that gets shredded a lot, and a great ass. His character development from money-grubbing media whore to tragic genuine hero doesn't hurt either.
While Sin City is mostly known for it's women, Frank Miller adds plenty of Male Frontal Nudity from all of its male protagonists (with the exception of Marv). Dwight was even shirtless for the entire Big Fat Kill miniseries.
In the Den series, Den and any other male human becomes this upon arrival in Neverwhere, naked, muscled and hung, albeit bald.
Tony Stark could have very well made his fortune by getting a nickel for every time he ends up naked, tied up, brainwashed, imperiled, or otherwise put into situations that give the fangirls squee-fodder. There is at least one blog solely dedicated to all the times the various incarnations of Tony end up at least half-nude, and it's quite large.