Billionaire Investor Stanley Druckenmiller is among the best investors of all time. During the fourth quarter, Druckenmiller swapped some of his holdings in the "Magnificent Seven" for other stocks in the elite group.

Duquesne Family Office's billionaire chief shed a trillion-dollar artificial intelligence (AI) stock in favor of a historically cheap drugmaker that's more than doubled in less than two years.

Warren Buffett once told shareholders,  “The worst sort of business is one that grows rapidly, requires significant capital to engender the growth, and then earns little or no money. Think airlines.” He continued,