There's never a shortage of losers in the stock market.

Let's take a closer look at five of this past week's biggest sinkers.

Company

Aug. 3 Weekly Loss My Watchlist
Halozyme Therapeutics (Nasdaq: HALO) $4.61 (53%) Add
Zipcar (Nasdaq: ZIP) $6.75 (39%) Add
Molycorp (NYSE: MCP) $11.49 (34%) Add
Dendreon (Nasdaq: DNDN) $4.45 (29%) Add
RealD (NYSE: RLD) $9.87 (23%) Add

Source: Barron's.

Halozyme Therapeutics was clobbered after the FDA rejected its drugs.

Zipcar went in reverse after the car-sharing service posted brutal quarterly results that missed Wall Street's top- and bottom-line targets. The leading provider of auto rentals by the hour also presented soft guidance for the current quarter.

Molycorp took a hit after stunning the market with a steep and unexpected quarterly loss. Sluggish prices for the company's rare-earth minerals are holding Molycorp back.

Cancer-drug developer Dendreon tumbled after posting a wide loss and announcing a cost-cutting plan that includes closing down one of its manufacturing facilities.

RealD screened a horror movie after posting a quarterly profit that clocked in at just a third of what analysts were expecting. Increasing costs and an unflattering mix of recycled 3-D eyewear in shipments slammed margins.

Ready for a bounce
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The Motley Fool owns shares of Zipcar and Dendreon. Motley Fool newsletter services have recommended buying shares of Zipcar. The Motley Fool has a disclosure policy. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. Try any of our Foolish newsletter services free for 30 days.

Longtime Fool contributor Rick Munarriz calls them as he sees them. He does not own shares in any of the stocks in this story, except for Zipcar. Rick is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early.