The HTC One is a great phone, and there are plenty of reasons to buy it. If you need just one more reason to push you over the edge, this may be it. HTC is offering $25 in Google Play cash to buyers, and it's easy to redeem. Some restrictions apply, as usual.
If you've got your HTC One in hand, head over to HTC's registration site. Enter your name, email address, and serial number. The serial number is on the original box and also in the Phone Identity settings. Assuming the information is correct, a Google Play code will arrive in your email inbox within 72 hours.
Strangely, this promo is not available to users who bought the One before yesterday. Devices must be purchased between 6/14 and 7/15 to get the free Google Play money. This is also a US-only deal, but it doesn't appear to matter where you buy the phone as long as it is in the US.