My pick for worse Atari 2600 game was "Swordquest: Earthworld" ( http://en.wikipedia.org/wiki/Swordquest ). The only redeeming feature that monstrosity had was the mini comic book that came with it. Once I had gotten the hang of playing ET, I actually used to enjoy it as a diversion from time to time. There were certainly less pleasant games in my library.
Oh, but the SwordQuest video games are at the heart of one of the greatest gaming mysteries out there. As you might recall, the games were released as part of a contest in which you would gather clues, and those who completed the game fastest were flown to Atari to compete for some really expensive prizes. The winner of Earthworld received a Talisman. The winner of Fireworld received a chalice. The winners of Waterworld and Airworld were supposed to receive a philosopher's stone and crown, respectively, but Atari was sold and those contests never took place. Each of those prizes were custom designed by the Franklin Mint and made of genuine 18k gold, silver, platinum, and precious jewels, and each was valued at $25,000. Ultimately, the winners of the four contests were supposed to compete for the Sword of Ultimate Sorcery, a real sword made of silver with a hilt of jewel-encrusted solid 18k gold, worth $50,000.
The thing is, in spite of the Waterworld and Airworld contests never happening and the final contest being canceled, those prizes existed. They were on display at the Fireworld contest, witnessed by the competitors there. Today, the remaining prizes are probably worth between approximately $150,000 and $200,000, not even accounting for the collectible value of them, which might push them up way more.
The mystery is, what happened to them? No one knows, or at least if they do, they're not telling.
Some speculate that when Atari was sold, the prizes were part of the package, and they might be sitting in a warehouse of stuff somewhere completely forgotten. Or someone might have known that they were valuable and taken them and sold them to collectors who have no idea what they are. Some speculate that Atari melted them down for the value of the raw materials. One popular theory is that the guy who bought Atari, Jack Tramiel, kept the items in his personal collection. Some have said that he kept the sword hanging in his living room, but no one has any evidence of it. He died a few years back and no word (that I'm aware of) has been issued on the subject.
As for the contestants, the winners of the first two contests agreed to be paid $15,000 each as compensation for not being able to compete in the final contest, and the contenders for the Waterworld contest were paid $2,000 each. As for the original two prizes, the talisman was said to have been melted down by the winner of the Earthworld contest to help pay for his college expenses, with him keeping a miniature sword that was part of it as a keepsake. The owner of the chalice still has it, and keeps it in a safe deposit box here in Atlanta, Georgia.
But whatever became of the Philosopher's Stone, the Crown, and the Sword of Ultimate Sorcery? Do they still exist, and if so, who has them?
That remains to this day one of gaming's biggest mysteries.
More info
here and
here, and Angry Video Game Nerd even talked about the games and the contest in
a YouTube video.