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

Feb. 3 Weekly Loss My Watchlist
MannKind (Nasdaq: MNKD) $2.17 (34%) Add
Hyperdynamics (NYSE: HDY) $240 (29%) Add
RadioShack (NYSE: RSH) $7.39 (27%) Add
ShoreTel (Nasdaq: SHOR) $5.40 (24%) Add
Polypore (NYSE: PPO) $46.83 (17%) Add

Source: Barron's.

MannKind was the market's biggest loser, shedding a little more than a third of its value after announcing a dilutive stock offering. MannKind's run into a few speed bumps -- and apparently now a cash crunch -- in getting its inhaled insulin Afrezza on the market.

Hyperdynamics was the Big Board's biggest decliner. It too announced a dilutive share offering at a healthy market discount, and that was enough to prompt Howard Weil to downgrade shares of the oil explorer.

Small-box retailer RadioShack got even smaller after announcing dreadful preliminary results for the holiday quarter. Thinning gross margins find the consumer electronics chain targeting a profit of no more than $0.13 a share for the holiday quarter, well short of the $0.37 a share that analysts were targeting.

ShoreTel may have posted a surprising quarterly profit, but it was the provider of Web-based telephony's bleak near-term outlook that led to investors hanging up on the stock.

Finally, Polypore took a hit after a former customer revealed plans to compete with the company by building its own plant to make filtration membranes. A couple of analysts downgraded Polypore on the news.

It was a rough week for these five stocks. If you want to shake yesterday's losers and ride tomorrow's winners, a new special report reveals Motley Fool's top stock for 2012. It's free, but only for a limited time, so check it out now.

The Motley Fool owns shares of RadioShack. Motley Fool newsletter services have recommended buying shares of Polypore International. 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.

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