A work of art
The Power Mac G4 Cube, released in 2000, was not a commercial success. Marketed as a small, affordable Mac, it was nonetheless more expensive and less expandable than equivalent desktop models and lacked the inbuilt monitor of the iMac. These limitations were compounded by flaws in its manufacturing that led to cracks in the case.
Nonetheless, the G4 Cube was an essential step toward development of the Mac mini. It also represents Apple's focus on revolutionary design: a G4 Cube resides in the New York Museum of Modern Art.
(Photo courtesy Steve Shaner, licensed under Creative Commons Attribution ShareAlike 2.0.)