If you ordered/order and activate your HTC one between 6/14/13 and 7/15/13, you can recieve a $25 Google Play gift card by registering at:
HTC Google Play
HTC will then send you a confirmation code that you can redeem through the Play Store!
Some are reporting that if your One was activated earlier than 6/14/13, you will still receive a $25 credit!
I tried it. We'll see if I get anything. (Bought a new One yesterday!)