Some stocks are one-hit wonders, making a big splash when they first appear, then quickly fizzling into obscurity or oblivion. But for other stocks, that initial big move is only a preview for even bigger and better gains to come.

Today, we've listed three stocks that made some of the biggest upward moves over the past month, which we'll pair with the ratings issued by our Motley Fool CAPS community. The higher each stock's rating, the greater CAPS members' faith in that company's ability to keep on beating the market.

Stock

30-Day % Change*

CAPS Rating

Mariner Energy (NYSE: ME)

74.23%

***

Javelin Pharmaceuticals (NYSE: JAV)

66.41%

****

Rexahn Pharmaceuticals (NYSE: RNN)

54.38%

*

*From March 26 to April 19.

As the markets whipsaw to changes in consumer sentiment, there will be weeks like this one when we see gains that are exceptionally ahead of the pace of the movers and shakers of prior weeks. So before we get shaken out again, let's see why the CAPS community thinks some of these companies might continue to outperform the market.

A mighty temblor
Nothing like a buyout offer to cause a big spike in a stock's price, and that's what we're seeing with Mariner Energy, which just got bought out by Apache (NYSE: APA) for $3.9 billion, including debt. While that accounts for the surge in its stock price, it follows on the acquisition of Arena Resources by SandRidge Energy (NYSE: SD) for $1.6 billion.

The important takeaway is we're likely to see more such buyouts of smaller E&P plays in an arena that's already awash in deals. The markets are feeling exuberant again these days, and the continued fault lines in natural gas pricing makes the smaller operators look more attractive. Range Resources (NYSE: RRC) or Cabot Oil & Gas might find themselves in some larger company's crosshairs.

No doubt some investors were already thinking along those lines, as more than 95% of the CAPS members rating the E&P shop believed it would outperform the market. Why not head over to the CAPS page of your favorite independent oil and gas company and drill down on whether or not it's a potential target, too?

Still feeling the aftershocks
And it was a merger agreement that caused Javelin Pharmaceuticals' stock to jump up as well. Medical products maker Hospira offered $145 million for the company, saying its post-surgery pain management drug candidate Dyloject was a good fit to market alongside its own sedation therapy, which is targeted to anesthesiologists. It looks as though the company served its shareholders well, as Javelin had previously agreed to a merger with Myriad Pharmaceuticals that would have netted $95 million, but could have reached as much as $115 million if certain milestones for Dyloject were met.

With its pain treatment accepted for formal review by the FDA, Javelin undoubtedly realized it had a hot property on its hands, and it leaves one wondering whether someone else (or Myriad) will come back with an even higher offer. Hospira, after all, has some FDA issues of its own to contend with these days, having received a warning letter about two of its manufacturing facilities.

The health-care industry, and pharmaceuticals in particular, is another area that's been hot for M&A activity, though it's been more a tale of megamergers like Merck and Schering-Plough or Pfizer and Wyeth.

Let us know on the Javelin Pharmaceuticals CAPS page whether you think someone else might have an eye for its pain management drug.

And thereby hangs a tale
It wasn't merger movements that got Rexahn Pharmaceuticals' stock moving higher, but CAPS All-Star biotech guru zzlangerhans channels the Bard in suggesting the lady doth protest too much after announcing its experiment depression drug Serdaxin failed to meet its main clinical trial goals. Despite not meeting its initial goals, Rexahn will continue to study the drug because it has already seen positive results versus a placebo. Zzlangerhans proclaims:

3. Out, damn'd spot! Out, I say!

Enter now our own Lady Macbeth, Chang Ahn, with a press release to address the inability of the market to understand the purpose or results of the Serdaxin phase IIa trial. Ahn points out that the purpose of the trial was never designed to achieve statistical significance, but rather proof-of-concept. I guess they got exactly what they wanted. Are your hands clean yet?

He cautions against being greedy with this stock else your profits die a death as grisly as that of Macbeth. If you've been lucky enough to make money here, you'd do well to take it and run. Or, as Shakespeare wrote, "No profit grows where no pleasure is taken; In brief, sir, study what you most affect."

Get thee to a nunnery, or at least the Rexahn Pharmaceuticals CAPS page, where it's no trouble at all to find out what this portends for the company's future.

Shake, rattle, and roll
With these stocks shaking the market this past month, it pays to start your own research on them at Motley Fool CAPS. Read a company's financial reports, scrutinize key data and charts, and examine the comments your fellow investors have made -- all from a stock's CAPS page.

Pfizer is a Motley Fool Inside Value selection. Try any of our Foolish newsletter services today, free for 30 days.

Fool contributor Rich Duprey does not have a financial position in any of the stocks mentioned in this article. You can see his holdings. You can shake, rattle, and roll The Motley Fool's disclosure policy, but it still won't break.