One from the What If Only Dept
Im sure many people will remember the CD Drive add on for the Snes that Nintendo eventually turned down and what was released later as the PSX(PSOne) well on our Dreamcast site theres a post about a prototype Disc drive for the Dreamcast. If only it had been mass produced then we could have had a fantastic option for what remains one of the very best homebrew scenes.
More details at DC News
Makes you wonder what other prototypes have been shelved that were actually decent.