Skype is quite the handy application in my household. Above all else it lets my parents see their Granddaughter once a week; even if she is usually covered in oatmeal.
And it's fun. The bright blue sky palette bursts with random flourishes of colour and the simple, whimsical illustrations scream possibility.
This attention to design is reflected across all aspects of the product. The website bursts with colour and shapes, the logo is a cloud-like shape embossed with the letter S. The startup sound is fun and other-worldly. Even the install window on the Mac continues to impress.
Simple design elements executed to perfection across the entire experience. It doesn't get much better.