The recent sharp drop in the overall stock market may have spooked some investors, leaving them on the sidelines for now. On the other hand, there are likely some opportunistic people willing to deploy capital into the market during this time. After all, famed investor Warren Buffett has often urged investors to "be greedy when others are fearful" in order to take advantage of great investment opportunities.

Consider Buffett's stance on stocks in October 2008, in the heat of the financial crisis sell-off. "The financial world is a mess, both in the United States and abroad. Its problems, moreover, have been leaking into the general economy, and the leaks are now turning into a gusher," wrote the Oracle of Omaha in a New York Times op-ed. "In the near term, unemployment will rise, business activity will falter and headlines will continue to be scary. So ... I've been buying American stocks." 

This is the sort of contrarian view investors need to succeed over the long haul. It's not easy, but it can be rewarding. Since Buffett wrote these words, the S&P 500 is up 173%.

For investors searching for good buying opportunities during this market downturn, here are two to consider: Costco Wholesale (NASDAQ:COST) and Twitter (NYSE:TWTR).

A grocery cart in the aisle of a wholesale store

Image source: Getty Images.

Twitter

Twitter has lost nearly a quarter of its value since Feb. 19, when the recent market downturn started to gain momentum.

It wasn't surprising to see pressure on the social network's stock price during this coronavirus pandemic. After all, as many retailers shut their doors and some manufacturers paused production, it stands to reason that some advertisers would reduce their spending. Indeed, the company confirmed in a March 23 press release that its ad revenue was taking a hit. Management revised its first-quarter guidance, saying it expected revenue to be slightly lower than in the year-ago period. Previously, management was expecting first-quarter revenue to rise 5% to 12%. 

But the silver lining in Twitter's March 23 update was that user growth saw a boost from the outbreak. Quarter-to-date monetizable daily active users were 164 million, up 23% year over year. This jump in daily active users highlights what makes Twitter such a great long-term investment. The platform is quickly gaining traction as the go-to platform for discussing timely news, such as the coronavirus outbreak.

While this global event happens to be a negative factor for advertising, these are unusual circumstances. When COVID-19's negative impact on the economy fades into the rearview mirror, advertising spend should pick back up and Twitter will likely have a larger base of daily active users than ever before for marketers to target.

Costco

Unlike Twitter, Costco's business seems to be a beneficiary from this pandemic. While many businesses have closed their doors during the coronavirus outbreak, grocery stores and wholesale clubs like Costco have remained open. Even in states with orders to stay at home, grocers have been deemed an essential business and remain open. Consumers have flocked to grocery stores and warehouses like Costco, stocking up on items and ultimately buying more inventory than the companies can keep up with. It wasn't surprising, therefore, when Costco said in its February sales update that it benefited from an uptick in consumer demand during the final week of the period. 

But Costco's sales were already growing nicely before consumers felt the need to stock up on extra items. For the four weeks ended Feb. 2, for instance, comparable-store sales (when excluding changes in gasoline prices and foreign exchange rates), rose 5.3% year over year, and e-commerce comparable-store sales during this same period rose 17%. Going further back, adjusted comparable-store sales for the five weeks ended Jan. 5, 2020, rose 7.8%, with e-commerce sales soaring 43% over this same timeframe.

Before this pandemic, therefore, Costco's business was already benefiting from strong customer loyalty and momentum from growing demand for bulk items at great prices. The company will likely continue retaining customers and winning over new customers for years to come. This pandemic simply illustrates how valuable Costco's business is to consumers.

Despite a likely jump in sales as a result of the pandemic, Costco shares are actually down 12% since Feb. 19, giving investors an attractive buying opportunity into a great business.

Of course, there's no guarantee these stocks won't fall further during these unusual times. But for investors willing to hold for the long haul, both Twitter and Costco look like stocks that could reward investors nicely from these levels.