Sega Master System
They sold poorly in the USA even though they were more advanced than the NES. I was one of the few that ever owned one.
They were so popular in the 1980′s a video game and cartoon was made about them. The only place I know that has them these days is Ebay.
My Buddy Doll
I never owned one; something about being a doll I never liked. However, millions of other boys did.