The S&P 500 surged 2.1% last week to 1,217.28, after investors bid the market higher on upbeat data on the housing market, strong earnings, and Greece's formal request for aid.

Pops and drops
Here are the five biggest S&P 500 upticks and five biggest S&P 500 drops of last week (measured Friday close to Friday close):

Winners of the week:

Company

Percentage Gain on the Week

Huntington Bancshares (Nasdaq: HBAN)

29%

Marshall & Ilsley

21.2%

Lennar (NYSE: LEN)

19.7%

PulteGroup (NYSE: PHM)

18.8%

SanDisk

18.2%

Source: Capital IQ (a division of Standard & Poor's).

Losers of the week:

Company

Percentage Loss on the Week

Baxter International (NYSE: BAX)

(16.5%)

AK Steel (NYSE: AKS)

(11.6%)

QUALCOMM (Nasdaq: QCOM)

(10.5%)

King Pharmaceuticals

(9.8%)

Gilead Sciences (Nasdaq: GILD)

(8.8%)

Source: Capital IQ (a division of Standard & Poor's).

A closer look
Shares of Huntington Bancshares roared last week, after the regional bank reported that it swung back to a profit in the first quarter, helped by a tax benefit and a reduction in loan losses. Excluding the tax benefit, the bank reported a quarterly loss; however, it was much narrower than analysts expected. Net charge-offs were nearly cut in half year over year. With credit losses easing, the company says it expects to report a profit for the full year. The bank was also upgraded by Keefe Bruyette and Stifel Nicolaus to "market perform" and "buy," respectively, from "underperform" and "hold."

On the downside, shares of Baxter International were hammered last week, after the medical-supply company lowered its earnings outlook for 2010. The downsizing owes to an increase in costs from the health-care bill, as well as weak demand for the company's plasma products, which account for 20% of the company's revenue. Adding insult to injury, the Food & Drug Administration is considering imposing new requirements for pump infusions (devices that deliver fluids such as medication and nutrients), which would affect Baxter.

In other health-care company news, shares of Gilead took a hit last week, after the biopharmaceutical company said it reduced its sales outlook for the year.

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Fool contributor Jennifer Schonberger does not own shares of any of the companies mentioned in this article. You can follow her on Twitter. The Motley Fool has a disclosure policy.