Mario Kart 64
This Mario Kart racing game was developed by Nintendo for the Nintendo 64. Critical reception upon release was divisive—critics either loved the game or found it to be extremely disappointing. If you held onto a vintage cartridge of this popular videogame from 1997, it could be worth up to $750 these days.
Barbie
You've certainly heard of Barbie, the fashion doll that has served as a quintessential cornerstone of the American toy market for over fifty years. Since 1959, Barbie has grown into Mattel's largest and most profitable line. You better start digging through the attic—an original Barbie is worth $23,000.