The AppleGazette has compiled a list of 5 Apple products
that were prototyped but never made it into mass production. I'm sure the basement at Cupertino is just filled to the gills with prototype iPhones and Mac Tablets that were never meant to be.
The five prototypes highlighted are the Apple PowerBop, Apple Paladin, W.A.L.T, Apple Videophone PDA, and Apple PenLite (pictured to the right). More info about all of these prototypes, and more, can be found at the Apple Museum.