When it comes to writing your subject line, we always recommend telling what’s inside, not selling what’s inside. Of course you need to sell (that’s the whole point) but you can’t expect a mere witty subject line to get people to open. That’s because we all play "whack-a-mole" whenever we check our email. We click "Check email" then we place our mouse cursor on the "this is spam" button and wait for all the junk we’re about to get. Admit it—you give new email about a half-second to prove it’s not spam.
So in your subject lines, you need to tell people 1) who sent the email, and 2) what’s inside the email (see: Subject Lines That Make People Open).
But that doesn’t mean you can’t have fun with your subject lines. I wuv the way W Hotels wrote their subject line in this Valentine’s Day email campaign (note how they tell you who sent it, subliminally reminding me that I did indeed opt-in for this email, and that it’s not spam, plus they injected a little personality):