What investors have witnessed over the past four weeks is nothing short of the most unprecedented volatility ever seen in the stock market.

Over a 19-session stretch between Feb. 24 and March 19, the 123-year-old Dow Jones Industrial Average (DJINDICES:^DJI) registered nine of its 11 largest point declines in history, as well as five of its six biggest single-day point increases. Aside from just nominal point moves, the Dow also recorded two its five largest single-day percentage declines in history.

For short-term traders it's been like walking through a minefield. But for long-term-oriented investors, the unfortunate spread of coronavirus disease 2019 (COVID-19) has created an incredible opportunity to buy into high-quality businesses on the cheap. Remember, no matter how dismal the outlook of every previous correction or bear market, the major stock indexes have eventually pushed to new highs on the back of bull-market rallies. That'll be the case with this steep drop-off in equity valuations, too.

With that being said, if you have even $2,000 in disposable cash -- i.e., cash you don't need to pay bills or for emergencies -- now is the time to put it to work. Here are four of the best stocks you should buy right now.

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Amazon

In case you haven't been paying attention, e-commerce giant Amazon.com (NASDAQ:AMZN) has held up far better than most companies during the coronavirus crash. This likely has to do with Amazon accounting for an estimated 38% of the U.S. e-commerce market, according to a June 2019 report from eMarketer. With so many consumers staying home to mitigate the spread of COVID-19, yet still in need of food and other household goods, Amazon is likely a very popular shopping destination.

But Amazon's long-term story is about far more than online retail or even its Prime membership, which has done an incredible job of keeping consumers loyal to the brand. The real growth driver here is Amazon Web Services (AWS). Amazon's cloud services sport substantially higher margins than e-commerce, which means that as AWS' percentage of total company sales rises, so will Amazon's operating income and cash flow.

Speaking of cash flow, this is where the real "cheapness" of Amazon stands out. Over the past decade, this company has been consistently valued at 23 to 37 times its cash flow. But based on Wall Street's 2023 consensus, which assumes superior AWS sales growth, Amazon is valued at less than 10 times its cash flow. I've said it before and I'll say it again: Amazon to $5,000 by 2023 is totally feasible.

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Johnson & Johnson

Healthcare conglomerate Johnson & Johnson (NYSE:JNJ) has also outperformed the broader market during this steep downtrend, but that doesn't make it any less palatable for long-term investors.

Johnson & Johnson sports a laundry of list of accomplishments that show why it's not being hit as hard as its peers. It's grown its adjusted operating earnings in 36 consecutive years, has raised its dividend for 57 consecutive years, and is one of only two publicly traded companies that still sports the coveted AAA credit rating from Standard & Poor's. The latter is meaningful, as it signals S&P has more faith in J&J to repay its debts than it does of the U.S. government making good on its outstanding debts.

Johnson & Johnson's secret sauce continues to be its three operating segments and how they each bring something important to the table. Consumer healthcare products, for instance, is usually J&J's slowest-growing segment, but it provides the most predictable cash flow and strong pricing power in most economic environments. Then there's medical devices, which has struggled recently with commoditization, but should have a long growth runway with an aging global population and improving access to medical care. Lastly, pharmaceuticals provide the bulk of J&J's margins and growth, but offer a finite period of exclusivity.

With a forward price-to-earnings ratio of 13, J&J is the cheapest it's been since 2012.

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JPMorgan Chase

Money-center banks like JPMorgan Chase (NYSE:JPM) have been on most folks' avoid list of late, primarily because banking is a cyclical industry. With a recession looking likely, this may reduce loan activity and up delinquency rates on existing loans. Further, the Federal Reserve cutting its federal funds rate by 150 basis points this month is bound to reduce the net interest income that banks like JPMorgan are bringing in. But none of these shorter-term worries should keep investors from taking their $2,000 (or more) in disposable cash and putting it to work in JPMorgan Chase stock.

This has been one of the most efficiently run banks since the financial crisis. With the exception of U.S. Bancorp, JPMorgan Chase has consistently been at or near the top among national money-center banks when it comes return on assets.

It's also been doing things a bit differently than its peers by opening, rather than closing, physical branches. This doesn't mean it's lagged on digital banking and mobile-app investments by any means, so much as demonstrates that JPMorgan Chase is still finding communities where it can offer its financial services and improve its market share.

Even with banking growth expected to slow, JPMorgan at less than 8 times Wall Street's consensus EPS for 2021, and only 12% above its book value, is a bargain.

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Alphabet

Another FAANG stock that should be on investors' buy list is Alphabet (NASDAQ:GOOG)(NASDAQ:GOOGL), the company behind dominant search platform Google, and popular streaming service YouTube.

The immediate worry for a company like Alphabet is that it generates the bulk of its revenue from advertising. Though these ad dollars are potentially less likely to dry up with consumers staying home to mitigate the spread of coronavirus and likely spending plenty of time online, history has shown that recessions pretty much always lead to ad spending declining.

However, this short-term pain isn't much of a worry for long-term investors. That's because Google has what looks to be an insurmountable lead in search (about 92% of global market share, as of February 2020), and is seeing its ancillary operations really begin to ramp up. Between 2017 and 2019, Alphabet saw Google Cloud sales more than double -- cloud margins are much higher than traditional advertising margins -- while YouTube ad revenue grew about 86%. As these faster-growing, higher-margin revenue dollars become a greater part of total sales, Alphabet should see a notable acceleration in cash-flow generation.

Similar to Amazon, Alphabet is valued at what would be a historically low multiple of a little more than 8 times its cash flow for 2023, making it a no-brainer buy right now.