The file
A toy oven that actually cooked, heated by a light bulb. The cakes were the size of a hockey puck, the mixes were mostly sugar, and the first one you made was the best thing you'd ever tasted.
It sold in the tens of millions across every design change, from the '60s turquoise to the '80s microwave-styled one. The bulb was retired in the 2000s, which older Gen X regards as a loss.
Sources: Wikipedia — Easy-Bake Oven