Just Gil? Tarvek isn't half bad himself. Hell, even Higgs is getting attention as of late. And Klaus has his groupies too. Let's just say that the Foglios know what their audience likes to see.
The first page of the Cinderella arc includes Gil and Tarvek debating their various EBB qualities. They seem pretty evenly matched, which might be why Cinderella!Agatha ends up with both princes.
Hell, even some of the Jägers have fangirls, with Maxim and Oggie having the most enthusiastic followings.
Maxim was originally an experiment to see if they could draw a Bishōnen Jägermonster. They pretty much succeeded.
Grrl Power is fairly open about the fact that most of the characters, male and female, are going to provide some fanservice at some point, and this is lampshaded in The Rant, and occasionally in the strip.
Name just about any male character from Hanna Is Not a Boy's Name and you will find a large female fanbase. The artist seems to have a special talent for drawing attractive men for every taste.
Slick Giovanni from Last Res0rt. Troubled past? Check. Former mafia don? Check. Looks good in harem gear? CHECK, PLEASE!
He's also naked on his mugshot.
Punch an' Pie, while not notably emphasizing the attractiveness of is female characters, gives us Aiden - the buff, nice hair sporting, tattooed Stoic.
Either Cale or Tavor from Looking for Group. While everyone agrees that Richard is Bad Ass enough to have everyone squealing, the fangirls tend to be split between the two elves.
Some of the guys El Goonish Shive. Elliot's a big muscular hero who has almost every girl (and Justin) at the very least admitting that they find him attractive. Tedd, when he takes off his glasses, shocks everyone with his uncomfortably girlish good looks.
The Adventures of Dr. McNinja: The titular Dr. McNinja is found attractive by a lot of viewers anyway, but Chris Hastings made it even more intentional with this. As the Alt Text reads: "Lil' bit of fan service for you ladies out there."
Male characters (okay, most characters generally) in Ménage ā 3 tend to be Hollywood Homely at worst, and most get topless or naked shots. The artist/co-writer's personal favorite male character — not specifically for this reason — seems to be Dillon, who eventually got his own comic, Sticky Dilly Buns, where he could get more screen time — some of it with his shirt off.
Hamlet Machine'sStarfighteris pretty much full of this, from main characters Cain and Abel (codenames, not a horribly cruel and unusual coincidence) give a lot of this, considering the NSFW nature of the comic and Cain's hobby of jerking off in his Starfighter craft.
In UC, Naim, tends to lose his shirt a lot, much to the fans delight.
In Accursed Dragon, half-dragon Coven is seen as a monster by most people within the comic, but the fans appreciate all the times he loses his shirt, gets stripped to his underwear, or is forced into a bath.
Sandra on the Rocks: The character of Domenico is probably parodying the trope during his frequent shirtless or near-shirtless scenes — not that he'd admit any such thing, and he has a distinct effect on women within the comic regardless.