The Subway gnomes!
These little bronze dudes are scattered all over several stations, I think; especially Union Square. Love ‘em. I’m always noticing a new one, tucked away in a place you wouldn’t see at first.
Update: Found the background on these! The series is called “Life Underground”, by Tom Otterness. You can learn more about it here and here, and see some more great photos at Flickr and at nycsubway.org.