I have a confession to make: I don't use ringtones. Most of the time, my phone is on vibrate, and when it's not, I insist that my ringtones actually ring. However, if I were to use custom ringtones, Ringtonium is the app I'd use to set them up. This app is beautiful. In a way that few apps are. The interface is brilliantly easy to use and accessible to even the most tech illiterate users.
Very similarly to turntable, this app might remind some folks of iOS just a bit, although this is more due to a design philosophy than any particular UI element.