I have a virgin mobile. It's pretty good. Has a built-in mp3 player. It takes a mini-sd card and you can put songs on it. The only down side is youtube is horrible. You can't go back, and it scratches if it doesn't have good reception. I do the $35 plan (unlimited text, 300 minutes of talk).
iPhone 4s has been my favorite however the big downside is the battery does not last! I sure hope they have worked on this problem with the iPhone 5. It only last 3 maybe 4 hours. Apple has admitted that this is a big flaw in their design.