When governments need money, they often go for a new tax wherever the money is. That makes sense, even when it is flagrantly unfair or even corrupt. But sometimes a tax can be used as a method for changing behavior, which was the impetus for a Russian tax on beards a few hundred years ago.
It's often claimed that King Henry VIII of England introduced a tax on beards, despite there being no records to prove it. Russia's Peter the Great, however, did place a tax on his bearded subjects. In 1698, in a bid to bring Russia up to speed with Western Europe's trend for cleaner shaves, he imposed an annual beard tax. His poorer subjects were allowed to wear a beard for just two kopeks a year, while wealthy citizens had to pay 100 rubles. Bearded tax-dodgers could be forcibly shaved by the police, while those who paid the tax were given a copper token to carry, which proved that their beard was fully paid for.
Whatever the reason, there have been some pretty strange taxes imposed on various societies throughout history. Read about taxes imposed on single men, political enemies, and urine, among other things at Mental Floss.