a mythical male creature who is successful (read: pursuing his passion and can pay his electric bills/rent), funny, chivalrous, masculine (read: not chauvinistic), adventurous, artistic (read: not suicidal).
See any John Cusack film (or Chuck Klosterman's witty commentary on Fake Love in Sex, Drugs and Cocoa Pops), any romantic comedy where the flawed guy comes through in the end...
"Where is my manicorn? I keep going out with all these losers!"
"Too bad I settled when I got married, I just met my manicorn."