Green Man Gaming just released a coupon, JOLLY-BRUCE-WAYNE, that gives a whopping 60% discount on Batman: Arkham City for PC.
After the discount, the price comes to just $17.75. I haven't heard of a better deal, anywhere.
Scoop it up while you can.
EDIT: CODE HAS EXPIRED. I posted this yesterday, the minute the deal went live. There was apparently a problem with the picture I uploaded, so it didn't get approved until today. Sorry for the inconvenience.