Son uses Samsung Flight. Daughter uses Samsung Strive.
Honestly, it would be easier to make recommendations if we knew a little more about how you intend to use the phone. What's important to you? Are you going to use it for just phone calls? Texting? Do you want a full QWERTY keyboard? Touchscreen? Are you upgrading through AT&T? Are you buying from some other outside source (such as Amazon or Ebay)? Direct from manufacturer? How much are you willing to spend?
More information would get you better recommendations.