Rainy Day National Oil Fund
All the money earned from oil and petrol taxes in Norway are added to the world's biggest sovereign wealth fund. As of January 2014, that piggy bank was full to the brim with 5.11 trillion crowns or $828 billion. The fund is being saved for a rainy day and to aid future generations once the oil is depleted. It currently owns 1% of all the world's stocks and makes every single one of the 5 million citizens of Norway a millionaire.
BTW, #18 is not 100% true. We pay more taxes than we need to the rest of the year to compensate for this. This is an old odd thing created so people could have more money for Christmas.