Okay, so I'm shamefully cheap. I picked it up from the Humble Bundle, so i'm not exactly breaking the bank here, but still...
Anyway, to be eligible to win said code (it's on Steam), you must answer the riddle set by the Riddler:
"What has a head, a tail but never any legs?"
Leave the real answer or a joke answer in the comments and the best one gets the code. Or just buy the Humbled Bundle, you know like the upstanding citizen you are.
I'll send you a PM, and oh yeah, if nobody replies then I'll just keep it for myself.
LOOK WHO CAME: