At ID school, as we learned about interfaces one of my professors explained that aspirin pills are mostly powder; the active ingredient is too small to handle, and the bulk of the pill exists simply so you can pick it up.
I don't know whether or not he got the same lesson, but Tianrui Xie, an Industrial Design student at the Georgia Institute of Technology, realized the same thing about computer mice. The "active ingredient" is the laser and the button(s), and the rest of it is just a palm-sized piece of plastic.
Xie then designed this Morph Wireless Mouse concept:
In addition to using less plastic than a traditional mouse, the concept would wield the power of digital fabrication to make each product better suited to the individual user. Xie's vision is that users would scan their mouse hand, and software would generate a custom-fit pattern that would be sent to a laser cutter.
The surface of the mouse would be, intriguingly, leather: "I thought of using 2mm thick veg-tanned leather as the substitution material for the traditional ABS plastic. It is flexible and sturdy enough at the same to achieve the transition from two-dimensional to three-dimensional."
Great work, Xie!
Worth noting: As mentioned, Xie is an ID student at Georgia Tech, but he designed the Morph while enrolled in the Offsite – Advanced Design program. Check 'em out!