Perhaps surprisingly, the Swedish giant Ikea wins the award as the greatest tax avoider in the world. Through numerous shell companies and a couple charities, the business is structured so that the sales and assets belong to a non-taxed charity, while the trademarks and other intangibles are privately-owned by shell companies headquartered in various tax havens. The net effect is that the charity spends very little money while being tightly controlled by the founder and the profits of the shell companies that earn the profits pay a whopping 2.5% tax rate on their profits.
See the Economist article (from 2006, but it was news to me).