The Infamous Sega Genesis CD drive. In response to The TG16's CD add-on Sega quickly developed this thing to jump on the Multimedia bandwagon of the early 90's. The CD offered advanced sound and graphics capabilities to the core Genesis console (most notably more colors and limited scaling and rotation.) But with most add-ons of this type sales were poor, not to mention a $299 price tag. This was 1990. CD ROM was still a new thing back then. There weren't even really affordable CD Rom Drives for home computers (not like today where you can get one for twenty bucks.)
Software in the beginning looked promising, then quickly degenerated into full motion crap and disappointing extended versions of normal Genesis games (like Mortal Kombat, which was essentially unchanged except for footage from the commercials and better sound.) Eventually this system became an experimental platform for developers to try new game concepts like that Penn and Teller game where the whole idea is to play practical jokes on a friend or something (the full title escapes me at the moment.) There are some pretty good games for this system, like Sonic CD and Eternal Champions, but overall the Sega CD disappoints. Maybe one day if I find it cheap enough I'll get one.