Investors have been nervous about the stock market's nearly straight-up movement over the past several months, as stocks have been remarkably resilient even in the face of past bad news. But today's onslaught of troubling items -- ranging from slowing Chinese economic growth and a nearly 10% plunge in gold prices to the deadly explosions at the Boston Marathon -- were enough to provoke a massive sell-off on Wall Street, with the Dow Jones Industrials (DJINDICES:^DJI) closing down 266 points. The S&P 500 dropped more than 2%, and the small-cap Russell 2000 Index suffered a nearly 4% decline.

Not a single Dow component managed to post even the tiniest of gains, but a couple of stocks minimized their losses. Wal-Mart (NYSE:WMT) finished down 0.1%, fulfilling its traditional role of holding up well as a defensive stock in light of potential threats to future economic growth. The company announced that it would boost its energy efficiency and commitment to renewable energy in an attempt to cut costs, but the discount retailer's strong performance in past recessionary times is likely the real reason behind its managing to hold up well today.

Far from a traditional defensive stock, Microsoft (NASDAQ:MSFT) limited its losses to a third of a percent today. With the company slated to announce earnings later this week, investors have just about the lowest expectations possible for Microsoft, given the weakness in the PC industry recently and its already-known slow rollouts of its Surface tablet and Windows 8 operating system. Reports of a smartwatch today aren't likely to inspire any more confidence than its other past initiatives, but anything short of a completely dismal performance with its earnings could help the stock get at least a short-term bounce.

Outside the Dow, the big news came from Sprint Nextel (NYSE:S), which soared more than 13% after DISH Network (NASDAQ:DISH) made a competing bid for the company. The $25.5 billion DISH deal would involve Sprint shareholders getting $7 per share in compensation, with more than two-thirds of it coming in cash. Yet Sprint's stock soared above the $7 level, suggesting that investors expect a bidding war between DISH and previous bidder Softbank. Whether such a bidding war will materialize, of course, remains to be seen -- especially if adverse market conditions start to weigh on the overall mergers and acquisitions environment.

Fool contributor Dan Caplinger has no position in any stocks mentioned. You can follow him on Twitter @DanCaplinger. The Motley Fool owns shares of Microsoft. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.