If you have an old Atari 2600 in your attic, you's better go and dig it out right now.
The console itself isn't worth that much, because Atari sold millions of the things, but if you have a copy of the game Air Raid, you could well be minted.
According to Tweak Town, one lucky Texan read an article about rare Atari games and decided to have a look in his garage. What he found was a practically mint copy of the cartridge in its original packaging. As it turned out, it is one of only 13 in existence and the only one in its box.
He put the game on eBay and it recently sold for a whopping $31,600, that's more than 20 grand in real money.