Most of what people here have posted as "sexy" or "sexualized", I find utterly repulsive. I am female with an extremely high sex drive and prefer a man with some meat on him but not a "meat head".
This type of build and pose is sexier than one that is trying to hard:
or this one of Matt Damon:
http://us.cdn001.fansshare.com/photos/mattdamon/matt-damon-shirt-off-shirt-off-100161095.jpg
Now for actually being "sexualized", I don't think much outside of insinuating sex acts, positions, or masturbation as being all that sexualized. I am not seeing how they are sexualized by simply being shirtless, or even naked. Being sexy and being sexualized are entirely different.
I know this is a matter of taste, but I found the skinny anime guys grotesque looking and Johnny Depp mace worthy gross. Not because I do not like men or sex, In fact I LOVE men and daily sex, just those type of men repulse me.
Faces, body language, personality and a good smile are also very important, but if they are too bony or underweight, I have a hard time even looking at them without being grossed out.
If you want to have an actual "sexualized character" an erection would be a requirement I would think. Making men feminine or "like ken dolls" down there is definitely not what I would consider sexualized from a female POV.
Although this might be considered portraying a man as a "sex object":
Though I am not sure if that is a sex object more than it is a "desk".
Edit: This Hosiery ad with a woman walking naked men on a leash I would think would safely said to be sexualizing men.
http://4.bp.blogspot.com/_IxFbDVkq7a0/SM8ks4UjDOI/AAAAAAAAAGY/jmE3VIio7bs/s1600-h/voodoo_01.jpg
Oh and heres a good one!
Hercules captured by amazon women:
http://www.orgonebox.org/allegoric/wp-content/gallery/sorbo_kevin/hercules-amazon-women/hercules_amazon_wmn_(27).jpg