Just as we examine companies each week that may be rising past their fair value, we can also find companies potentially trading at bargain prices. While many investors would rather have nothing to do with companies tipping the scales at 52-week lows, I think it makes a lot of sense to determine whether the market has overreacted to the downside, just as we often do when the market reacts to the upside.

Here's a look at three fallen angels trading near their 52-week lows that could be worth buying.

A discount in plain view
It may not seem like it, but higher payroll taxes combined with the IRS furloughing its employees in order to save money, and thus delaying tax refunds for millions of Americans, really walloped the retail and grocery sector. Wal-Mart, the world's largest retail chain, reported a same-store sales decline of 1.4% in the first quarter. It blamed everything but the kitchen sink for its disappointing results, including inclement weather and little grocery inflation, but also alluded to higher payroll taxes and delayed tax refunds.

Much of the same can be said about The Pantry (NASDAQ: PTRY), a predominantly Southeastern U.S. convenience store chain that operates under the Kangaroo Express name. Food inflation has been minimal, the weather hasn't been as cooperative, and consumer traffic fell 4.6% in its most recent quarter. But where other investors see weakness, I see an opportunity.

For one thing, food inflation costs are rarely predictable, but they don't normally remain stagnant for long periods of time, either. As food costs inevitably push higher, The Pantry will be able to pass along price hikes to consumers and eke out slightly beefier margins. Even a single basis point is important in the margin-tight grocery business, so look for food inflation increases in the upcoming quarter to aid The Pantry's bottom line.

Taking a page right out of its larger counterparts, The Pantry is also emphasizing unique brands to push product out the door. From its self-branded Kangaroo gasoline to its exclusive Bean Street Coffee, the convenience chain is using unique brands to differentiate itself from its competition and drive higher sales. Although traffic was down last quarter (which I feel is a short-term issue caused by delayed tax refund checks), average sales per customer rose 2.6% -- not bad considering that food inflation is minimal. With the stock at just 11 times forward earnings, I see room for The Pantry to head higher.

You have the wrong idea
Seeing gold and other commodities fall off a cliff has admittedly given a lot of investors plenty of reasons to avoid resource-rich emerging-market countries. Over the past couple of months we've seen numerous emerging-market ETFs drop precipitously, all while the S&P 500 continues its march to new highs. One such ETF that's only bounced modestly off its lows is the Market Vectors Africa Index ETF (AFK 0.13%), which, as you might expect, invests in various African companies.

I freely admit that my first suspicion when I saw the drop over the past couple of weeks was that the ETF owned stock in a large number of mining companies. I mean, it would make sense to see the ETF retreat if metal prices are dropping and miners are shuttering production in the meantime. However, very little of the Market Vectors Africa Index is tied up in mining. Simply put, investors have the wrong idea about this ETF!

In actuality, this ETF is going to give you a porterhouse-size helping of banks and other financial services in Africa. As of June 30, nearly 37% of its holdings were in the financial sector, with another 18% in the necessity energy sector and another 13% in materials. In total, the fund owns 109 different companies that pay out a yield of 3.5% with a net expense ratio of just 0.8% annually. These sectors still have decades of double-digit growth opportunity in Africa, and I don't believe investors are giving them nearly enough credit.

I also would urge investors not to overreact to that fact that 25% of this ETF's investments are tied up in Egypt. Although regime change is often tumultuous, Egypt has the basic infrastructure in place to pick up growth right where it left off under now-deposed Egyptian President Mohamed Morsi. With investments in other more stable regions of Africa making up another good chunk of its remaining investments, I feel the Market Vectors Africa Index ETF could surprise investors moving forward.

Thinking really long-term
Sometimes we need to put on our Warren Buffett goggles and think like Buffett if we hope to find the market's best buy-and-hold opportunities. This week I feel could represent the perfect opportunity to nab shares of medical diagnostics company Quest Diagnostics (DGX 4.36%), which are still relatively close to a 52-week low.

The weakness in diagnostic companies lately can be blamed squarely on reduced government spending domestically and overseas. In addition to deriving revenue from biotechnology companies, Quest works with government agencies and universities that are funded by government money. With the U.S. instituting austerity measures designed to reduce its federal deficit, and much of Europe in a similar situation, diagnostic device makers have struggled to improve their top and bottom lines in recent quarters.

Looking long-term, though, there is an incredible demand for medical diagnostics. The baby boomer population is aging and diagnostic equipment is becoming faster, more accurate, and more affordable, meaning insurance companies are more likely to back diagnostic products now more than ever.

Consolidation in medical diagnostics also gives us visible clues to the sector's potential. For example, Thermo Fisher Scientific agreed in April to buy Life Technologies for a hefty $13.6 billion. In 2012 Life Technologies introduced a new bench-top molecular diagnostic tool that can analyze the human genome in 24 hours or less for just $1,000, proving how far molecular diagnostics has come in just two decades. Diagnostic companies like Life Technologies and Quest Diagnostics speak to a level of personalized medicine that is just starting to bloom and could be the basis of many treatments down the road.

Boasting a yield of 2% and a forward P/E under 13, I feel this is another great set-it-and-forget-it candidate.

Foolish roundup
Sometimes the trend really is our friend. For The Pantry, rarely are food inflation costs tame for a long period of time, which would bode well for its ability to raise its prices. With regard to the Market Vectors Africa Index ETF, it's about the potential for steady double-digit growth from a number of regions for decades to come. And finally, for Quest Diagnostics, it's about the increasing importance of personalized medical care moving forward.

I'm so confident that these three names will bounce off their lows that I'm going to make a CAPScall of outperform on each one.