Last Week's Biggest Stock Movers: GeekNet Soars, Kors Slumps

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Plenty of stocks go up and down in any given week. The gainers inspire us to keep investing. The decliners keep greed in check while reminding us about the risks of the equity markets.

Let's go over some of last week's best and worst performers.

GeekNet (GKNT) -- Up 152 percent last week

The market's biggest winner was GeekNet, soaring after a bidding war broke out for the parent company of the ThinkGeek online store specializing in all things geek. Where else can one get a Tardis waste bin or a pizza cutter shaped like Star Trek's U.S.S. Enterprise?

Goth apparel retailer Hot Topic kicked things off earlier in the week by announcing an offer to buy GeekNet for $17.50 a share. GeekNet received a rival offer for $20 a share later in the week, asking Hot Topic to top the offer Friday. We'll see where this battle ends in the coming days, but for now GeekNet's popping faster than you can say "Bazinga!"

ITT Educational Services (ESI) -- Up 76 percent last week

The for-profit post-secondary educator soared after providing audited financials for 2014. ITT confirmed that revenue took a 10 percent hit last year, and that's something that isn't really a surprise given how student enrollments have tailed off sharply at post-secondary institutions. It sees another 10 percent to 15 percent slide in enrollment for 2015.

However, ITT also came through with a profit of $1.23 a share for all of 2014. That's a lot more than analysts were forecasting. ITT may not be any closer to a turnaround, but at least it's not faring as badly as worrywarts had feared.

MannKind (MNKD) -- Up 15 percent last week

An upbeat analyst report on MannKind helped push the shares 13 percent higher a week earlier. It followed that up with a 15 percent pop last week after announcing that it would be making appearances at three different health-related investor conferences this week.

MannKind's been making waves since receiving FDA clearance to market Afrezza, an inhaled insulin that's growing popular with diabetics.

Michael Kors (KORS) -- Down 25 percent last week

It was a rough week for the maker of the once-trendy premium handbags. Kors took a hit after announcing the first year-over-year decline in comparable-store sales in its tenure as a public company.

It gets worse. Guidance for its current quarter suggests that comps will continue to be negative. Fashion can be fickle. Investors in Kors rival Coach (COH) saw it turn negative two years ago, and it has yet to bounce back. Now it's Kors that is suffering from waning popularity in the U.S. market.

United Rentals (URI) -- Down 15 percent last week

An analyst downgrade slammed shares of United Rentals. Bank of America Merrill Lynch lowered its rating on the stock to underperform -- and its price target to $80 -- on concerns that the renter of industrial and construction equipment is losing its pricing power. An oversupply of rental gear in the industry poses a threat to near-term results.

Shake Shack (SHAK) -- Down 11 percent last week

The rally in shares of Shake Shack took a breather last week. The stock had soared a week earlier after reports suggested that it might open up a sister chain specializing in chicken, but the real spike was likely the result of a short squeeze.

Given Shake Shack's thin float of shares available for trading and the high short positions, it's not a surprise to see any whiff of bullish news trigger a wave of shorts scrambling to cover their positions. That's been a big driver in the recent gain, but the rally came undone by the middle of last week with the stock giving back some of its earlier gains.

Motley Fool contributor Rick Munarriz has no position in any stocks mentioned. The Motley Fool recommends and owns shares of Coach and Michael Kors Holdings. Try any of our Foolish newsletter services free for 30 days. Check out our free report on one great stock to buy for 2015 and beyond.