Quote Originally Posted by J T View Post
I can think of a fair few that weren't particularly successful (well, in the gaming sphere at least): Mega CD, Sega 32X, N64DD (was pretty much abandoned never released properly) - not to mention the tons of gimmicky peripherals like the nintendo power glove.
Add-on wise, nothing I can think of. Peripherals, the only truly successful one I can think of was the Dual Shock. It took enough of the market from the original digital controller so that later games required it. Whether this counts I'm not sure as although it came 3 years after the PSX launched, it was bundled as standard with the console from late-1998 on.