Ringtones are so overrated. Door chimes are where it's at. The iChime allows you to play any of the included 50+ songs/sound effects (there is also an option to record 6 custom recordings that can be interchanged at any time) and a breeze to install with its simple two-wire replacement. Check out a demo of their built-in chimes here.
Dimensions are 5" x 7 3/4" x 2". Available for $89.95.