Since nobody mentioned it, I'll throw in the Adam, which was supposed to be Coleco's pivot into the home computer business, and was much-hyped back in the day for offering
the sun, the moon, and the stars for a cut-rate price:
Also, full backward compatibility with ColecoVision games! And platform exclusives! And an even cheaper upgrade kit for ColecoVision owners!
But the launch was delayed multiple times, and buyers figured out why: Just about every component was horribly unreliable, and included features like the ability to erase nearby data cassettes simply by turning the system on. The whole thing became a money pit, and Coleco eventually played the long con by offering, I shit you not, a $500 scholarship for every buyer with a kid under 18:
Coleco abandoned all video game development less than two years after the Adam launch, and went bankrupt a few years after that--presumably all unused scholarships from the Adam promotion were rendered null and void. And now you know...the rest of the story.