Singapore. They just removed their VAT on precious metals.
Dubai removed the VAT, income tax, corporate tax, sales tax, and property tax on everything... or more specifically, they never had them =) But, good on Singapore, that's very smart of them. If only they'd apply the logic consistently... if removing taxes on Good X makes country trading hub for Good X, then wouldn't removing taxes on all goods make country trading hub for all goods? Few of the world's brilliant leaders have ever been able to figure this out.