Warren Buffett's Berkshire Hathaway has made significant investments in three key stocks: Amazon, Visa, and Chubb. Amazon, the leading e-commerce and cloud company, has seen its value more than double since 2019, while Visa, a top card payments processor, has maintained strong growth through economic downturns. Chubb, the largest publicly traded insurance provider, has shown resilience with substantial gains in operating income and premiums, making it a stable choice amid market volatility.