Ikkaku's shirt goes missing when he unveils his Bankai, Hisagi never wears sleeves and gets nicely roughed up in his fight with Findor Carias. Kensei has several scenes exposing his lovely, muscular chest and arms...the list goes on and on. Hell, even Mayuri had a Shower Scene that showed that he's actually pretty hot under his weird makeup.
Sosuke Sagara is definitely the ultimate example for this show, though. He gets the most shirtless scenes, and in general is the one who is used when someone needs to look sexy.
All over the place in Arata Kangatari. While the manga's story and action are very Shounen, with a Japanese teenaged boy switching places with one from a parallel fantasy world and going on an adventure in a Wutai-style fantasy land, the author is Yuu Watase. She's known for her Shoujo work, so many of the male characters boast well-defined muscles and their costumes make them Walking Shirtless Scenes. Even the translator gets excited during the Hot Springs Episode, making jokes about how it included some of the best panels of her favorite characters.
Perfect Girl Evolution AKA The Wallflower has four guys each for a specific appeal; Kyohei seems to get the majority of the shirtlessness though.
In Kuroko no Basuke, pretty much all the guys are this. Considering that this is a sports-genre anime, this series has way more attractive male characters than other sports-genre series. From Kagami (with shirtless scene in episode one), Kise who works as a model, to Kuroko himself.
He also has a very naked bath scene where he's barely covered by strategic floating clumps of rose petals, in a slow pan from his feet to his head. And when he gets out of it, they pan as low as they can without showing "little Creed."
With Fushigi Yuugi, it's probably just easier to narrow down which male cast members aren't catering to some estrogen brigade bait fantasies. Whether your taste runs to Draco in Leather Pants (Nakago, Suboshi), or to gorgeous, gallant royalty (Hotohori), or to fiery redheads (Tasuki) or to your basic romantic hunk (Tamahome), there will be at least one ridiculously attractive male character who gets a) gratuitously wet, shirtless or both; and b) a sympathetic Back Story. Hell, even resident monk Chichiri gets in on the fanservice action.
Sechs from Battle Angel Alita: Last Order either fits the trope or is a parody of it. Starting out as a exact replica of the female main character, by volume 5 Sechs, after losing her original android body, has changed to a 1.8-metre-tall thin but muscular male body. This was either done to get more female readers into the series or to poke fun at the lack of attractive male fighters in the manga. Additionally, in volume 10 it's revealed that Sechs has gained a large female fanbase in the solar system, much to his/her annoyance.
Lockon Stratos both Neil and Lyle, thank you very much, from Gundam 00. Somehow, both Shinichiro Miki and Alex Zahara manage to do wonderful things with Lockon's voice. It's possible that because he fits this trope so wonderfully that so many fangirls forget what happens when his Berserk Button is pressed...
Then again, this trope can probably be used to point out almost every male character in the series, protagonists and antagonists alike. In A.D. 2307, humanity is still at war... but at least they all look good.
Although most of the male cast of Karneval could qualify to the point of being full of pretty boys, Gareki is especially seen in cut up or revealing outfits that should not look as hot as they do when he's wearing them.
Almost every single male character in Fruits Basket. Particularly Momiji, Yuki, Ayame and Kyou. The first wears the girl's school uniform (albeit not with a skirt) because "it looks cuter on him", and gets an Imagine Spot dedicated towards showing him aged-up as a Bishōnen. Yuki has soft grey hair and violet eyes, and made for a pretty convincing girl the time he's forced to wear a dress. Ayame is a white hair given quite a few Bishie Sparkle shots. Then there's Kyou, who fits more in the All Girls Want Bad Boys area, with a Hot-Blooded temper and tendency for dere dere moments around Tohru, and an apparent predilection for shirtlessness. The other males get their fair share of moments as well. Tohru lampshades this once, calling the Sohma family a "family of princes". Generally, the series — with its preference towards over-the-top romanticism and Dark and Troubled Pasts — aims more for making fangirls swoon rather than squeal, but the Sohma family curse's transformative effects lead to so much nudity that it still fits.
Don't forget Hatsuharu! Especially when he goes Black Haru.
If Black Butler's plot and gorgeous art doesn't keep you hooked on the series, the ridiculous amounts of Ho Yay fodder and gorgeous guys will. Special mention goes to Sebastian, who is, without a doubt, extremely badass, has silky shoulder-length black hair, is extremely tall and handsome, constantly wears black, has a somewhat sensual nature. And considering that his human looks are actually derived from Vincent Phantomhive's... Oh!
This is kind of the reason why Saint Seiya has a BIG female fanbase. The most obvious is probably Andromeda Shun, a Reluctant Warrior with a pretty face, in-universe fanclub and big brother complex. The storyline where he's possessed by the god of death doesn't help matters either.
Higurashi: When They Cry: Keiichi. Aside from his various… interesting (and quite exploitative) outfits, he gets a now-quite-infamous Guy on Guy Is Hot scene between him and Satoshi in the Kira OVA, which is drooled over In-Universe by the female cast. Apparently, his dad is also one in the manga.
Kiryuu Touga and Ohtori Akio in Revolutionary Girl Utena can often be seen in open shirts. Of course, some would say any onscreen appearance by Akio constitutes fanservice in itself...
Kaworu Nagisa from Neon Genesis Evangelion. Smooth voice, elegant, handsome, and for the few times he's appeared (counting the movies) usually he's either naked, giant and naked, wet, in bed with another guy or in any combination of those.
Minami from Cherry Juice, who has the natural harem, the non-chalant shirtless-ness, and who is not above kissing his bishonen best friend in order to make his sister jealous. His status as this trope is lampshaded within the manga with the opening line:
"A stylish man... dripping with sweat!"
07 Ghost: Mostly Frau and Teito, but considering what goes into becoming a Bishop...yeah. The antagonists definitely count as well (especially Ayanami).
In Hakuōki, nearly all of the high ranking members of the Shinsengumi are bishonen, with different members hitting all of the standard personality traits associated with this trope. Given the source material for the series, this shouldn't come as a surprise.
In Tiger & Bunny, Barnaby's in-universe status as raging fangirl-bait is something of a running gag.
Koutetsu: Don't you ever get tired of doing that that?
Barnaby: Doing what?
Approaching Fangirl: E-excuse me? Can I hold your hand?
In Wild Rock, a manga full of bishonen running around in Loin Cloths, Emba's design can be considered nothing more pure cheesecake fanservice. He's got the "manly, but caring" personality to boot.
Mobile Suit Gundam Wing: Despite being part of a franchise generally targeted at males (because girls can't possibly be entertained by giant robots and politics), an overwhelming majority of the fanbase was female; females who were unabashedly interested in the male characters of the show for their looks, with maybe personality coming in at a close second. Heero, Duo, Trowa, Quatre, Wufei, Zechs, and Treize all fit this trope. The sheer amount of fanfiction, doushinji and websites dedicated to them (usually of the HoYay nature) is testament. IIRC this was done intentionally to broaden their audience demographic. It worked.
On that note; there is PLENTY of Dark and Troubled Pasts (particularly Heero, Duo, Trowa and Zechs), Badasses (all of them), pretty boys, questionable moments that fuel the massive amount of yaoi fangirlism, stoicism (Heero and Trowa; although they kind of sorta not really get over their absolute stocism), jerks with hearts of gold, and a Shirtless Scene (maybe- Heero had bandages, but bandages aren't shirts, right?). Depending on your mileage there is Foe Yay (Zechs and Heero always promising to finish their "duel"). So much Woobie (depending on the character it may be Iron or Stoic) it is almost painful to watch at times, considering what the pilots have been through and what they keep going through during the show.
Kou from Monochrome Factor. Troubled past? Check. Emotional and physical scars? Check. Sexy voice? Check. Looks great with his shirt off? Check. Comfortable with man-on-man scenes? Check. Akira and Shirogane are also great examples.
While Fairy Tail rather blatantly caters to its male fans, it has one particular character by the name of Gray Fullbuster who, in addition to being the Only Sane Man, and having a tragic backstory, owns a very nice body which readers get plenty of chances to ogle, since his obligatory quirk is stripping to his boxers without realizing it. Hiro Mashima does not try to hide that attracting female fans is Gray's job. When the first major arc focused on Gray, he said it was due to the female fans: there weren't enough of them.
Natsu also qualifies as a Mr. Fanservice as his top consists solely of a vest, leaving his abs completely exposed. And Sting is always exposing his midriff.
Being a series about American football, Eyeshield Twenty One have wonderfully fit athletes working out, shirtless, or just looking attractive all over the place. Special mentions go to Shin, Agon, Kakei, Mizumachi, Akaba and Kotaro.
Fate/Zero's Lancer, Diarmuid ua Duibhne, which is an actual power of his thanks to his cursed Beauty Mark (which causes him tons of problems both in the original myth and in the show). The Einzbern Consultation Room short did not let this go un-lampshaded.
Zecchan: Why isn't there an otome game based on Celtic mythology yet?
Kill la Kill's Aikurō Mikisugi randomly slicks his hair back and removes his glasses to reveal his handsome face while also randomly undoing his clothes and striking erotic poses when he explains how Senketsu works to Ryuko. He does this for no reason other than to annoy Ryuko and make girls watching the show faint.
Hell, he even has fangirls who find his old man disguise sexy, despite it clearly not meant to be.
Gamagoori is this for Bara Genre fans. He spends a lot of time shirtless and the show loves drawing attention to his size and muscle mass.
Tsumugu for similar reasons. It helps that he's almost always near-nude.
Space Dandy has both Ms. Fanservice and Mr. Fanservice— Dandy himself filling the latter role, as one can see in episodes 6 and 8. In 'The War of the Undies and Vests, Baby' Dandy spends 98% of the episode in just his briefs, and in the second half of 'The Lonely Pooch Planet, Baby' we get not one but two pan-ups showing his bare butt, as well as him dressed in just a towel.