Most valuable toy: Mighty Max Skull Master ($150)
Original price: $10-$20
Selling for now: $1-$150

The Polly Pocket-style toy aimed at boys didn't have the staying power of the original, and it hasn't reached the same peak values. But, if you have the right vintage Mighty Max set laying around, you might be able to get a couple hundred for it if you play your cards right. If you were a completist back in the day, you might be able to cover most of a month's rent by selling your entire Mighty Max collection.