Recently, some internet person picked up an unmarked Game Boy game at retailer Hard-Off for a mere ¥105 (US$1.29). It's not actually unmarked, with the label scratched completely off. The cartridge's back reads "unko" or "crap" in Japanese.
Our brave shopper stuck the "crap" cartridge in his Game Boy Advance SP, flipped it on and discovered it was Pokémon: Blue, one of the first installments in the Pocket Monsters series (the other being Red). This game helped launch the whole Pokémon craze.
Toggling through the game's menu, the shopper discovered that the previous owner, "Takuya", had played the game for a mere 2 hours and 28 minutes, earning only one badge, before apparently flipping out. Worst two and half hours ever!
Takuya probably spent longer scratching the game's label off and carving "unko" in the cart than playing the game.