
Marc Jacobs used himself as the model for his new fragrance called BANG.
With an interview with Harper's Bazaar her explains why he is naked in the ad:
“I’m not 
Tom Ford  in terms of the grooming and the knowledge of clothes and the precision  and perfection of getting dressed. There’s nothing I can wear in this  ad that isn’t going to look ridiculous. At one point, I tried jeans and a  shirt, and it didn’t work. So then Juergen said, ‘Take off the  clothes.’ So I did, and that became the ad. I did feel good about the  way I looked, so it was easy and—well, a guy looks better to me with no  clothes on than with clothes! How’s that?”
Here is the website for the fragrance