Warren Buffett, Michael Burry of "The Big Short" fame, and other top-flight investors made significant changes to their stock portfolios in the first quarter of this year, ranging from a huge wager on Chevron to a bet against Apple. Ray Dalio, Jim Simons, and Stanley Druckenmiller's funds all made notable tweaks to their holdings. The first two bought or sold two of the best-known meme stocks, GameStop and AMC, while the third bet big on energy stocks and made a surprising wager against the S&P 500.