BALTIMORE (Stockpickr) -- Bored buyers finally woke up last week, catapulting the big S&P 500 index 2.7% higher. After churning sideways for all of 2015, U.S. markets are finally back within grabbing distance of new all-time highs. Not surprisingly, that's creating some big buying opportunities in some of Wall Street's biggest stocks.

Year-to-date, the S&P has rallied all of 2.39%, which means that stocks only popped their collective heads above the surface last week. Until then, the big stock indices were under water. But, then again, this is hardly uncharted territory. Last year was extremely similar in structure to what we're seeing now: Stocks corrected hard in January, followed by a swift rebound in February and then some sideways churning in March.

Then again, the S&P closed the year with 11.4% gains in 2014. If 2015 is a repeat performance, it could be a whole lot worse.

To take full advantage of the upside potential in stocks, we're turning to a fresh set of Rocket Stocks worth buying this week.

For the uninitiated, "Rocket Stocks" are our list of companies with short-term gain catalysts and longer-term growth potential. To find them, I run a weekly quantitative screen that seeks out stocks with a combination of analyst upgrades and positive earnings surprises to identify rising analyst expectations, a bullish signal for stocks in any market. After all, where analysts' expectations are increasing, institutional cash often follows. In the last 291 weeks, our weekly list of five plays has outperformed the S&P 500's record run by 83.26%.

Without further ado, here's a look at this week's Rocket Stocks.

Actavis

Up first is generic drug giant Actavis (ACT) - Get Report. While 2015 has been a fairly flat year so far for the broad market averages, it's been anything but flat for Actavis. Since the calendar flipped to January, ACT has rallied more than 23%, leaving the rest of the market in its dust. As momentum continues to plow higher in the pharmaceutical sector, Actavis is well-positioned to keep its upward trajectory.

Actavis is one of the largest drug companies on the planet, a position it's achieved through a series of high-profile acquisitions. Historically, most of Actavis' volume has been in the generic drug business, but that changed with the close of the Allergan acquisition last week. Now branded drugs make up more than half of the combined firm's sales. Allergan's portfolio of niche treatments should be a nice complement to Actavis' generics portfolio, and the firm should still mitigate most of its patent loss risks.

After all, Actavis actually expands its offerings when drugs fall off patents, boosting sales through the release of new off-label versions. Likewise, Allergan's blockbuster Botox brand comes with household-name consumer awareness and loyalty. After some integration costs, expect the savings from a much bigger Actavis to work their way to shareholders' pockets.

Foot Locker

$9 billion athletic apparel retailer Foot Locker (FL) - Get Report is anther stock that's shown investors a double-digit performance already in 2015. Since the start of the year, it has rallied 11.6%. Foot Locker tips the scales as one of the biggest sellers of footwear and athletic apparel, selling through a network of 3,460 stores worldwide. Besides its namesake brand, Foot Locker operates stores under another eight brands, from Champs Sports to Runners Point.

Foot Locker's positioning in the specialty retail business is attractive -- finally. After a long stretch of underperformance for mall stores, Foot Locker is starting to benefit from an uptick in consumer spending again. While big sports brands such as Nike (NKE) - Get Report do have pricing power over retailers, Foot Locker's scale still gives it some leverage with smaller vendors.

From a financial standpoint, Foot Locker is in great shape. The firm currently carries $833 million in net cash on its balance sheet, enough to pay for more than 9% of its own market capitalization at today's price levels. That big cash cushion is a big risk reducer right now, and it brings FL's earnings multiple down to a pretty middle-of-the-road 15.

With rising analyst sentiment in shares this week, we're betting on this Rocket Stock.

Starwood Hotels & Resorts Worldwide

The travel business has been picking up in the last two years, and, not surprisingly, that's been a very good thing for Starwood Hotels & Resorts Worldwide (HOT) . Starwood operates more than 1,200 luxury and premium hotels spread across nine different brands. The firm's chains include Sheraton, Westin, W and St. Regis. As the upper end of the travel industry continues to get a disproportionate share of growth, HOT looks well-positioned for 2015.

Overwhelmingly, Starwood is only the hotel operator, not the owner. Instead, third parties own 95% of the firm's locations, which are still run by HOT. The result is a relatively asset-light business that generates meaningful returns on assets while avoiding the balance sheet leverage and market risk that comes with owning a huge real estate portfolio. Because Starwood doesn't allow franchisors to run the properties themselves, it's able to provide a consistent experience for guests, which is a critical part of commanding premium pricing.

Starwood makes long-term deals with its property-owners, so the firm's locations are extremely sticky. The switching costs of changing brands are exorbitant, and rarely make much sense for landlords. HOT's margins have consistently landed in the double-digits, and that number should continue to grow as occupancy rates continue to slowly climb and the firm commands a higher price tag for each room it sells.

We'll get our next glimpse at HOT's numbers when it reports first-quarter data at the end of April.

Rackspace Hosting

Rackspace Hosting (RAX) helps its customers put their data in the cloud. Rackspace is a managed hosting provider, selling space on its servers -- and the infrastructure and know-how that keeps those servers online 24/7. By using Rackspace for their co-location and cloud storage needs, firms can save considerable money versus doing it all in-house, a fact that helped RAX generate $1.7 billion in revenues last year.

Rackspace benefits from the tailwind of growing server needs. Because more and more enterprise data and services are moving online, a rising tide is lifting all ships in the hosting space, particularly those with specialized and value-added offerings that RAX can provide. Rackspace has an impressive customer Rolodex that's remained strong thanks to an active sales organization. As long as the firm continues spending on its sales force, it should maintain an edge over competitors trying to poach big clients.

That sales organization is also key to operating leverage at Rackspace. As the firm expands its menu of products and services, a sales team that's deeply knowledgeable about customers' needs should be able to convert more existing customers to new offerings.

RAX is far from cheap at current valuations, but momentum is clearly on the side of buyers right now.

Analog Devices

So far, 2015 has been kind to investors in Analog Devices (ADI) - Get Report. Shares have rallied more than 10% since the beginning of January, leaving the rest of the market in its dust. That outperformance has been welcome too. Like other semiconductor stocks, ADI has seen a mixed bag of performance in recent years, but it's been one of the most consistent performers of the group.

A lot of ADI's relative strength has to do with what it makes. Analog Devices is the leader in the market for chips that translate between analog and digital signals, which gives them a role in everything from cell phones to cars. In total, ADI serves more than 60,000 customers worldwide, a broad customer base that exempts the firm from worrying about the fortunes or decisions of a single major customer. Because ADI's chips are just a necessary afterthought in most consumer devices, competition is relatively low. OEMs would rather just buy them than engineer and build them.

ADI is another cash-rich name on our list – the firm currently carries more than $2 billion on its balance sheet, enough to cover about 10% of its shares at current levels. With rising analyst sentiment in ADI this week, we're betting on shares of this Rocket Stock.

Author had no positions in stocks mentioned.