Warren Buffett, Michael Burry, and other top investors just published their Q2 stock portfolios. Here are 5 key trades they made.

Buffett's Berkshire Hathaway took a knife to its pharmaceutical holdings last quarter. It sold around $260 million of AbbVie stock, $307 million of Bristol Myers Squibb stock, and $645 million of Merck stock, based on the companies' average closing share prices in the period.

The famed investor's company only bought into the trio in the third quarter of 2020, and boosted its holdings in the fourth quarter. Yet Berkshire turned around and sold roughly $2.4 billion worth of pharma stocks in the first six months of this year, slashing its AbbVie and Bristol Myers Squibb stakes by about 20% and its Merck position by 68%.

While Buffett has been interested in owning a basket of pharma stocks for decades, he hinted in May that he didn't fully understand them and wasn't too comfortable holding them. That may explain the recent disposals.

Michael Burry of "The Big Short" fame purchased bearish put options against 235,500 shares of Cathie Wood's flagship exchange-traded fund Ark Innovation last quarter.

The Scion Asset Management chief tweeted in February that the hype around Wood had reached excessive levels. He compared her to past growth investors whose luck ran out, and warned that "Wall Street will be ruthless in the end."

Burry also ramped up his bet against Tesla last quarter. Elon Musk's electric-vehicle company is one of Ark's biggest holdings, underscoring Burry's skepticism of the mass disruption and technological revolution that Wood believes is coming.

The Scion chief is best known for predicting the collapse of the housing bubble in the mid-2000s, and making a fortune by betting on that outcome. He also helped pave the way for the GameStop short squeeze in January by investing in the video-game retailer and agitating for changes at the company back in 2019.

Bill Miller's fund, Miller Value Partners, bought around 122,000 shares of Coinbase worth $30 million last quarter. The investment underscores Miller's continued faith in cryptocurrencies and the larger blockchain ecosystem.

Miller made his fortune as a value investor before losing 90% of it during the financial crisis. However, he's a billionaire today thanks to early investments in Amazon stock and bitcoin.

Notably, his fund sold its GameStop shares before the video-game retailer's stock went stratospheric in January, meaning it missed out on a massive windfall.

Jim Simons' Renaissance Technologies tapped into the meme-stock boom last quarter with a well-timed bet on AMC Entertainment.

The quantitative hedge fund, founded by the Cold War codebreaker and MIT math professor in 1978, tripled its stake in AMC in the three months to June 30. The movie-theater chain's stock price skyrocketed nearly 500% in the period as retail investors piled in. As a result, RenTech's position jumped nearly 20-fold in value to $103 million.

In contrast, RenTech slashed its stake in Tesla by 75% last quarter, reducing the value of its position to $138 million at the end of June.

The Church of Jesus Christ of Latter-day Saints took its GameStop profits off the table last quarter.

Ensign Peak Advisors, the church's $100 billion investment fund, invested in GameStop in the fourth quarter of 2020. The value of its position ballooned by about 900% in the first three months of the year thanks to the short squeeze on the stock.

Ensign didn't list GameStop in its latest portfolio update, suggesting the fund cashed out the stake last quarter. It likely pocketed about $9 million from the exit, based on GameStop's average closing share price in the period, or as much as $14 million it if sold when the stock surged in June.