Here’s something you’d probably never think of:

[…] a self-enforcing protocol for determining property tax: the homeowner decides the value of the property and calculates the resultant tax, and the government can either accept the tax or buy the home for that price. Sounds unrealistic, but the Greek government implemented exactly that system for the taxation of antiquities. It was the easiest way to motivate people to accurately report the value of antiquities.

It seems counterintuitive, but when you think about it, it makes perfect sense. The (short) article can be found here; it’s worth a read.