Without question, 2020 is going down as a year that Wall Street and retail investors are never going to forget.

The spread of the coronavirus disease 2019 (COVID-19), a respiratory illness that's responsible for the deaths of more than 46,400 people around the world as of April 1, represents not only a direct threat to the physical well-being of people but also their financial well-being.

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You see, mitigation efforts being enacted in many U.S. states, as well as developed countries throughout the world, are designed to flatten the curve and ensure that our healthcare systems don't become overwhelmed. However, these mitigation efforts call for the near-halt of nonessential economic activity. In other words, the cure to the coronavirus comes at a sizable short-term cost to the U.S. and global economy. It's this uncertainty that pushed equities to the fastest bear market in history, as well as registered the worst first quarter in the 123-year history of the Dow Jones Industrial Average.

Then again, history that shows that perceived-to-be abysmal scenarios have always been buying opportunities for long-term investors. No matter how steep or prolonged a bear market has been in the past, a bull-market rally has eventually come along to wipe away the entirety of the move lower. The key is that people have to remain invested in high-quality businesses and allow their investment theses to play out in order to take part in this historical push higher in the major U.S. indexes.

In short, as the stock market has crashed, smart investors are taking their disposable income and putting it to work in companies with clear-cut competitive advantages.

The thing is, you don't need to have Warren Buffett's pocketbook to be an investor in this market. With virtually all brokerages eliminating commissions, it's easier than ever to put $1,000 in disposable income to work. Below you'll find three top stocks that smart investors are almost certainly buying right now with their $1,000 (or more) in spare cash.

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AT&T

Perhaps one of the most surprising casualties of the coronavirus crash is telecom giant AT&T (NYSE:T), which has lost more than a quarter of its value. AT&T is a highly defensive name with a low beta, meaning it doesn't tend to be very volatile in relation to the S&P 500.

So, why the angst surrounding AT&T, you ask? The likely reason is the expectation of additional cord-cutting as the unemployment rate rises and COVID-19 forces families to make some spending cuts. With ownership of DirecTV, and having completed the buyout of Time Warner in 2018, an expedited exodus from cable would certainly provide a temporary sting. Not to mention, AT&T also announced it would halt its share buyback program for the time being to preserve its premier dividend.

Let's be clear -- none of this is good news in the very near term. But looking at the bigger picture there's a lot to be excited about. For instance, AT&T is in the midst of rolling out 5G networks across the country. This is the first major wireless infrastructure upgrade in about a decade, and it's liable to lead to a multiyear tech-upgrade cycle. Since data is what drives the company's wireless margins, and the vast majority of its wireless customers are on subscription plans (which yield low churn rates), its wireless division should be a source of solid organic growth in the years to come.

Also, don't overlook AT&T's streaming assets. The upcoming launch of HBO Max, and the addition of Time Warner's prized assets (TNT, TBS, and CNN), may be enough to lure consumers away from competitors, and will help to offset revenue declines from cord-cutting.

At only 7 times forward earnings, and sporting a 7.4% yield, AT&T is looking like a must-own for value- and income-oriented investors.

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Visa

Now, if growth is your thing, don't turn a blind eye to payment processor Visa (NYSE:V), which is undoubtedly a stock that smart investors are loading up on.

In general, payment facilitators have been crushed during the COVID-19 crash. The concern here being that purchase volume will drop off big-time as consumers are forced to stay home. Further, as unemployment tied to stay-at-home mandates increases, there exists the possibility of a rising wave of loan and credit delinquencies.

While these are tangible concerns for credit-service providers, they aren't nearly as worrisome for Visa as they are for some of its peers. For starters, it's because Visa isn't a lender. Unlike some other payment facilitators that also choose to lend, Visa purely sticks to processing transactions for merchants. This means if loan and credit delinquencies do rise, Visa will only be indirectly impacted.

Another key point being that Visa holds the lion's share of the U.S. credit card market by network purchase volume. Between the height of the financial crisis and 2018, Visa managed to increase its share of U.S. network purchase volume on credit cards by 11 percentage points to 53%. When the U.S. economy comes roaring back, which is a virtual certainty, Visa is going to be in excellent position to benefit.

This is a company that can grow at a double-digit percentage, annually, in an expansionary economy -- and the economy spends far more time expanding than contracting. Remember that!

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Intuitive Surgical

Smart investors will also be putting $1,000 or more to work in business with incredible moats. Surgical-assisted robotics company Intuitive Surgical (NASDAQ:ISRG), my top investment idea for April, is one that certainly comes to mind.

Intuitive Surgical is likely to contend with some very near-term weakness as elective surgical procedures are pushed back by hospitals, surgical centers, and insurers. This is being done to keep presumably healthy people out of hospitals and ensure that only the sickest folks with COVID-19 are getting beds.

However, it's important to recognize that the coronavirus isn't a long-term issue, and Intuitive Surgical's broad competitive advantages will soon shine through. For instance, the company ended 2019 with over 5,580 da Vinci surgical systems installed around the world. None of its competitors are even close to this figure, even on a combined basis. These surgical systems tend to be pricey ($0.5 million and $2.5 million) and they require quite a bit of training for surgeons, which means hospitals and surgical centers that buy one tend to remain longtime clients.

But the best aspect of Intuitive Surgical's business model is that it's built to grow stronger over time. Although its da Vinci systems are pricey, the revenue derived from these systems tends to generate relatively low margins. After all, building a complex system for precise surgeries isn't cheap. The bulk of Intuitive Surgical's gross margin comes from the instruments and accessories sold with each procedure, as well as the servicing done on already installed da Vinci systems. As the company's installed base widens, these higher-margin segments will grow into a larger percentage of total sales, thereby boosting profits at a much faster rate than sales growth.