Volatile stocks can produce some downright wonderful returns, but the risks can be equally heart-stopping. To help guide you through the wilderness of high-risk, high-return investments, we asked three Motley Fool contributors to become your investment Sherpas.

Among their recommendations, you'll find wireless upstart Sierra Wireless (NASDAQ:SWIR) rubbing shoulders with eternal turnaround story Sprint (NYSE:S). Tesla Motors (NASDAQ:TSLA) rounds out the roll call, offering fantastic returns for investors with decades of patience -- and buckets full of antacids.

Anders Bylund (Sprint): I'll admit that buying Sprint isn't for the faint of heart. Share prices have plunged 56% in 2014, as rivals of both the larger and hungrier varieties poach subscribers from the company. On the surface, Sprint shares seem doomed for continued weakness.

Sprint CEO Marcelo Claure has his work cut out for him. Source: Sprint.

But I think that's a much smaller risk than the Sprint bears would argue. The stock is actually primed for a huge rebound from these deep-discount levels.

The wireless carrier is equipped with a brand new CEO, an entrepreneur with experience building billion-dollar businesses from the ground up. And CEO Marcelo Claure is backed with the full faith and confidence of Softbank CEO Masayoshi Son, including his endless bankroll. Son turned Softbank around in the Japanese market, amassing his billions in epic fashion with low-cost service plans and early access to hit devices like the first Apple iPhone in Japan.

I don't know what tricks Claure and Son might have up their sleeves for 2015 beyond the recently announced half-off promotion. But I do know that Sprint will bid aggressively in the upcoming wireless spectrum auctions and that the leading carriers should have plenty of reason to sweat over the reformed Sprint. I haven't yet picked up Sprint shares for myself, but this turnaround potential is making my trigger finger mighty itchy.

Tamara Walsh (Tesla Motors): The upstart electric-car maker is undoubtedly one of the most disruptive companies in the world today. However, Tesla's future growth comes with tremendous uncertainty. For starters, the California-based company faces seemingly endless execution risks with respect to its massive battery factory. Earlier this year, Tesla named Nevada as the home for its planned Gigafactory, but the company is still in the early stages of the build out. Slated to be the largest lithium-ion battery plant in the world, Tesla needs its Gigafactory operational by 2020 if it hopes to reach its production goal of 500,000 vehicles a year.

The stock's sky-high valuation is yet another reason why Tesla Motors makes for a risky play. Shares are currently trading around $223, with a price-to-sales ratio of 10 times -- meaning Tesla investors are paying roughly $10 for every $1 of sales today. Such lofty market expectations for the company create another layer of risk for investors. Therefore, even the smallest setback could result in a major sell-off.

However, for high-risk investors with at least a 10-year time horizon, Tesla Motors might end up being one of the greatest long-term bets in many investors' portfolios. The company's innovative battery technology has the potential to transform both the automotive industry and the solar energy industry going forward. Tesla's global Supercharger Network is a competitive advantage that sets the EV maker apart from rivals in the auto market. For these reasons and more, Tesla Motors is currently one of the best stocks to consider for high-risk investors.

Alex Planes (Sierra Wireless): Imagine getting into the best Internet stocks 20 years ago just as the web was starting to take off. Well, that opportunity is here again, and it lies in the Internet of Things, or IoT. Sierra Wireless is widely considered to be a leader in this small but fast-growing field.

The upside and downside for Sierra are similar to those faced by many early Internet companies. If it succeeds, Sierra should grow by orders of magnitude, becoming one of the leading purveyors of critical hardware for a massive industry like a Cisco for the Internet of Things -- anyone who followed Cisco in the '90s will remember just how rapidly the company grew during that time, on both a fundamental and share-price basis:

CSCO Chart

CSCO data by YCharts.

Sierra boasted an industry-leading 34% market share in machine-to-machine (M2M) embedded modules at the end of 2013. These modules are essential components in the IoT -- they're the pieces of hardware that connect the "things" to the Internet in the first place and thus provide those things with their marching orders, so to speak.

By 2020, the market for connected devices is expected to grow anywhere from 9 times to 35 times larger than it was in 2012, according to several reports. With this growth, just maintaining its market share would give Sierra that order-of-magnitude growth we're looking for. If Sierra can expand its slice of the market, that would truly add some fuel to the opportunity. This could parallel Cisco's story, as the company grew so quickly by increasing its market share throughout the '90s to emerge as the dominant player in the routers-and-switches arena.

However, Cisco never had to contend with the large hardware companies Sierra currently faces in the semiconductor industry. The M2M market is currently dominated by smaller players -- Sierra joins Germany's Gemalto and London's Telit to control about two-thirds of worldwide M2M sales, or about $1 billion between the three companies. Combined, they are worth less than $10 billion, and most of that market value comes from Gemalto's non-M2M operations. Competition from low-cost Chinese chipmakers or dominant connectivity-chip companies like Qualcomm could erode Sierra's pricing power and dampen its growth, if not stall it out entirely.

The upside potential is huge as is the risk. Investors interested in pursuing Sierra should think hard about how much they're willing to bet on the company's ability to maintain its market leadership in the coming years.

Alex Planes owns shares of Sierra Wireless. Anders Bylund owns shares of Tesla Motors. Tamara Rutter owns shares of Apple and Tesla Motors. The Motley Fool recommends Apple, Cisco Systems, Sierra Wireless, and Tesla Motors. The Motley Fool owns shares of Apple, Qualcomm, Sierra Wireless, and Tesla Motors. 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.