Last month was another tough one for the markets, with the S&P 500 falling 9%. Year to date, the index has now plummeted 24% and taken many quality stocks down along with it. The good news for long-term investors is that many beaten-down stocks won't stay down for long. That means buying today, as perilous as the situation may look, could allow you to lock in some high-yielding stocks at cheap valuations.

Three dividend stocks that stand out as being among the most promising buys right now are Pfizer (PFE 0.56%)Suncor Energy (SU 0.65%), and Verizon Communications (VZ 0.43%). Here's why you should consider adding these stocks to your portfolio today.

1. Pfizer

Pharmaceutical giant Pfizer is down 26% this year, performing in line with the broader markets. However, given the popularity of its COVID-19 vaccine and the company's ability to adapt to changing conditions, it's a bit surprising that investors are only valuing the business at nine times earnings. Although its bottom line will likely decline as fears around the coronavirus continue to subside, its COVID-related revenue won't disappear entirely; health officials are still administering booster shots, and there's still no telling if and when that will end.

Plus, the low earnings multiple suggests that a lot of bearishness is built into the stock. But that shouldn't be the case because Pfizer has been busy acquiring multiple companies within the past year, expanding its business and making it more diversified for the future. In June, it closed on the purchase of ReViral, a clinical-stage company that focuses on therapeutics for the respiratory syncytial virus (RSV). Pfizer currently has multiple trials ongoing that relate to RSV.

And there will be more opportunities out there for the drugmaker. The company has a whopping $33.3 billion in cash and short-term investments on its books as of July 3. For a business that consistently generates positive free cash flow, Pfizer's in great shape to pursue growth opportunities while also paying a solid dividend, which yields 3.7% today -- more than double the S&P 500 average of 1.8%. Its low payout ratio of 31% also suggests Pfizer has plenty of room to boost its payout in the future. In the past five years, the company has increased its dividend by 25%.

Pfizer is a strong business with an expanding pipeline, tons of cash, and a solid yield. It's hard to go wrong with the stock, especially at its current low valuation.

2. Suncor Energy

Another top choice investors should consider is Canadian oil sands company Suncor Energy. At just under 5%, its dividend yield is even better than Pfizer's. Shares of Suncor have climbed 21% since the start of 2022 as rising oil prices have made investors more bullish on it and other oil and gas stocks.

In August, the company reported stellar Q2 results, with adjusted funds from operations totaling 5.3 billion Canadian dollars for the period ended June 30 -- a record figure for the business. The company also highlighted that its oil sands operations clocked record numbers for the second straight quarter, thanks to higher prices.

Suncor's shares have fallen in recent months because oil prices have also been declining. But investors shouldn't count out a rally, as the price of oil could remain elevated, especially given the war in Ukraine remains ongoing. But even with lower oil prices, Suncor could make for a great dividend stock with a payout ratio below 25%. And with a price-to-earnings ratio at just over five, investors aren't paying any premium for the stock right now.

For investors looking for a good stock to help offset the effects of inflation, Suncor could make for an excellent buy thanks to both its dividend and exposure to oil and gas.

3. Verizon Communications

The highest yield on this list belongs to Verizon. At 6.9%, this is a dividend stock that all income investors should be eyeing right now. This is not a typical yield for the company. The stock is down 25% this year, and that has resulted in a higher yield.

Its payout ratio is 51%, which isn't terribly high given the stock's seemingly astronomical yield. Although Verizon reduced its forecast earlier this year and its performance hasn't been in line with management's expectations, over the long run the telecom giant still makes for a top dividend stock to own. And this year, it projects that its wireless service revenue will grow between 8.5% and 9.5%.

Its P/E ratio is at around eight, which is cheap compared to the S&P 500, where the average stock trades at 18 times trailing profits.

Verizon may be one of the best dividend stocks to buy right now given its higher-than-usual yield. For long-term investors, buying it is a move that could pay off in droves.