I have to be honest. There are a lot of ways to describe a ride on NYC's subways, but "sexy" is NOT the first one that comes to mind. Refinery 29's recent slideshow disagrees.
Check our their street style snaps from "NYC's Sexiest Subway Routes."
In short, if you're single and trolling you should really focus on taking the 6 , the L and the N/R trains.
(images courtesy refinery 29)