Henry George

In a libertarian world, where do taxes come from? Income taxes violate the most fundamental of rights; the right of a person to his or her own body, and the labor that it produces. They also have the negative effect of disincentivising work; if people get to keep less of what they produce, they'll produce less, especially in a progressive income tax system, which punishes people for producing the most.

Sales taxes have the same problem; they punish people for trading, which is the last thing you want to do in a free market system. So do tarrifs, etc.

What remains is property tax. This is where Henry George comes in - to digress slightly, a problem with libertarian philosophy comes with the ownership of land. The ownership of private property, or anything that is the product of one's labor, can morally be assigned to whoever produced it, or whatever they traded the product of their labor for, etc. Land was produced by no one; natural resources were produced by no one. Therefore, the only way one can claim ownership of them is by showing up before anyone, or by using coersion to claim ownership. Neither is tenable under libertarian philosophy.

So, a legitimate form of government is the collection of rent from a resource that cannot be morally owned. A good primer for this is here.