Egg Box - No, it isn't software exactly. But it is a great example of a design that works well at revealing the beauty and nature of the content to the user rather than hiding it, which is what UX design ought to do more.
Cadbury's Creme Eggs. Shown here with their forerunner Border Eggs (the ones in the tartan wrappers). Creme Eggs in the 1970s were larger than they are today and the chocolate was thicker and the filling actually was nice, not like the revolting mixture nowadays.