We've all made plans to buy exciting stocks … and then never gotten around to it, letting multibaggers pass us by. But market volatility can often grant us second, third, or fourth chances at the stocks we missed. In a welcome silver lining, a market crash that depresses the prices of stocks we own also drives down the prices of stocks we wish we'd bought.

A surgical cut
For example, consider our "The Best Stocks of 2011" collection that ran at the end of 2010. We spotlighted Intuitive Surgical (Nasdaq: ISRG), which sells robotic surgical equipment to hospitals, then enjoys recurring revenue from instruments, accessories, and services for those robo-docs. This new medical niche has few publicly traded pure plays other than Intuitive, Hansen Medical (Nasdaq: HNSN), Stereotaxis, and MAKO Surgical (Nasdaq: MAKO). Investors impressed by Intuitive's prosects who bought shares late 2010 saw the company move from around $260 per share to $400.

But then the stock market took a dive. That didn't change Intuitive Surgical's business model or promise, but it did lower its price from above $400 to around $350 recently. (If you pounced quickly, you might have grabbed shares near $322.) The company's valuation remains compelling, with a P/E ratio below its five-year average. It might seem a tad pricey with its forward P/E of 26, but consider that its five-year average annual earnings growth rate is 33.5%. With some folks long speculating that it might get bought out by a company such as Johnson & Johnson, Intuitive Surgical's price has only become more attractive to prospective buyers. The company has seen growth in procedures performed with its machines slow a bit, but it's still growing briskly.

Up and down in smoke
Another stock for 2011 still looks promising for the rest of the year, despite having run up from a low of about $23 this year to $28 not so long ago. As a large, relatively stable blue chip, Altria (NYSE: MO) doesn't have quite the growth potential or growth rate as a company like Intuitive Surgical, but it's been one of the best wealth generators over much of the past century. As its year-end write-up noted, "Since 1970, Altria has returned 155,300% (including reinvested dividends), versus 4,500% for the S&P during the same period."

Its compelling (if morally iffy) business model involves selling smokes to people who simply have to have them. Admittedly, this investment may not appeal to everyone. Some will have justifiable qualms about cigarettes' toxic effects on their users, while others may note that higher U.S. taxes on cigarettes are driving people to quit, and stifling Altria's business. Big sales gains in the U.S. are a thing of the past, though tobacco use is likely to grow faster in developing nations. Investors keen on hardier growth may want to consider sister company Phillip Morris International instead.

On the plus side, Altria recently sported a 6% dividend yield, which far exceeds what you can earn from your bank, most CDs, and even most blue-chip dividend payers.

Changes of fortune
As you seek sudden opportunities, make sure you've done your homework before you buy. While some stocks plunge simply because the overall market did, others are actually struggling. One of the stocks for 2011, Dendreon (Nasdaq: DNDN), is a prime example.

Its FDA-approved prostate-cancer drug, Provenge, showed a lot of promise. But the drug's $93,000 price tag has proved to be a bit of a stumbling block, despite FDA and Medicare approval, and not all doctors are even aware of that Provenge has secured a regulatory thumbs-up. Sales have been disappointing, with expected annual revenue dropping from between $1.5 billion and $2 billion to between $500 million and $1.2 billion.

Some investors are now steering clear, aware that competitors are offering their own prostate-cancer treatments, such as Exelixis's (Nasdaq: EXEL) cabozantinib. Others worry that the company has been funding its drug development via dilutive secondary offerings, a tactic shared by other biotech companies such as Vertex Pharmaceuticals (Nasdaq: VRTX). But with Dendreon's stock down from near $40 only a month ago to less than $10 in early August, other investors see an overreaction and growth in the offing. They're also mulling the possibility that a bigger pharma company might buy Dendreon.

Watch that list
When the market takes a big tumble, and flocks of investors start heading for the hills, consider running in the other direction to grab shares of great stocks. Maintaining a watch list of such companies is a great way to monitor them all in one place.

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