Samsung Galaxy S3
Despite its age, and the impending arrival of the Samsung Galaxy S4, the AT&T Galaxy S4 remains one of the best options on Ma Bell's network.
Read: Samsung Galaxy S3 Review.
The Galaxy S3 sports a spacious HD display, a speedy processor, good cameras, Android 4.1 Jelly Bean and best of all, some high quality software courtesy of Samsung. It will also more than likely get Android 4.2 and perhaps Android 5.0 as well making it a fantastic option for those that don't need next-gen specs.
It's also cheap at Amazon as well, and a cheap on-contract price never hurt a smartphone buyer.