Everyone brace yourselves because the broad-based S&P 500 (SNPINDEX:^GSPC) is set to end the week down for the first time in a month. A mixture of profit-taking and concern that the Federal Reserve may wind down its bond-buying program sooner than expected has investors spooked.

The Fed's bond purchases create a sort of catch-22 for investors. On one hand, winding down its purchases would signal strength in the U.S. economy and point to it becoming more self-sufficient. Alternatively, fewer bond purchases could potentially move lending rates higher even with the Fed targeting record-low lending rates through 2015. In short, investor uncertainty has yielded another choppy, but modestly lower, reaction in the S&P 500.

When all was said and done, the S&P 500 ended lower by 0.91 points (-0.06%) to close at 1,649.60. There were few catalysts to send the market higher today, but the following three stocks certainly found the will to buck the downtrend in a big way.

Ascending to the top of the pack was robotic surgical device maker Intuitive Surgical (NASDAQ:ISRG), which gained 4.8% after winning a lawsuit involving its da Vinci surgical system. The plaintiff in the case was a family that sued for $4.9 million following complications from a 14-hour prostate cancer surgery. The jury's verdict isn't too important from a monetary perspective for Intuitive so much as it reinforces the safety of its surgical devices, which are currently under investigation by the federal regulators. I certainly feel there could be further upside in Intuitive shares from here.

The world's largest consumer products maker, Procter & Gamble (NYSE:PG), surged higher by 4% after announcing that Bob McDonald was retiring as CEO. More interestingly, former CEO A.G. Lafley, who was head of P&G from 2000 to 2009, has rejoined the company as its new CEO. Lafley was responsible for steadily growing P&G's core brands during his tenure, so shareholders seem very pleased to have him back. I can't help but be a bit excited as well because P&G's huge advertising campaign really hasn't hit home with consumers as of yet. I'd suspect the readdition of Lafley could move the company's marketing in a completely different direction, which would ultimately be beneficial to its bottom line.

Finally, advertising and marketing services company Omnicom Group (NYSE:OMC) added 3.4% despite no company-specific news today. However, earlier in the week, Omnicom announcement that it was keeping its dividend steady at $0.40 in the upcoming quarter certainly invigorated shareholders, who are digging Omnicom's 2.5% yield. Personally, I can't help but be a little skeptical of ad and marketing consultants in a slow-growing global environment, but shareholders are definitely enjoying a solid end to the week.

Fool contributor Sean Williams has no material interest in any companies mentioned in this article. You can follow him on CAPS under the screen name TMFUltraLong, track every pick he makes under the screen name TrackUltraLong, and check him out on Twitter, where he goes by the handle @TMFUltraLong.

The Motley Fool recommends and owns shares of Intuitive Surgical. It also recommends Procter & Gamble. 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.