NEW YORK (TheStreet) -- Heavy-hitting investors like Warren Buffett, George Soros and David Einhorn actively bought new stock positions last quarter, just as they were selling out of stocks they no longer deemed profitable, according to the most recent Securities and Exchange Commission 13F filings.

Hedge fund manager Julian Robertson sold much of his stake in Alibaba(BABA) - Get Report , the Chinese e-commerce company, however he boosted his position in Apple(AAPL) - Get Report , which represented nearly 7% of his portfolio at quarter's end. David Einhorn took a new position in Time Warner (TWX) , which represented more than 4% of his portfolio at quarter's end. And George Soros bought shares of LyondellBasell Industries(LYB) - Get Report as a new position that accounted for 2.5% of his portfolio. The filings were analyzed by GuruFocus.com, which tracks the buying and selling of so-called guru investors and top mutual fund managers.

Using data from GuruFocus, TheStreet looked at which shares had the most positive "impact" to investors' portfolios. GuruFocus defines impact as "the ration of the dollar value of the transaction relative to the total value of the portfolio," according to the Web site.

Check out which stakes investors like Warren Buffett, John Paulson, Daniel Loeb and others either bought for the first time or added last quarter and had the biggest impact on their portfolios. Note: The 13F filings report data as of Dec. 31, 2014. Any changes made since then will be reported in the first quarter filings.

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1.Warren Buffett
Berkshire Hathaway (BRK.A) - Get Report
Portfolio Size: $109.36 billion

Warren Buffett added shares of International Business Machines(IBM) - Get Report , which represented 0.95% of his portfolio at Dec. 31.

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2. John Paulson
Paulson & Co.
Portfolio Size: $19.36 billion

John Paulson bought into Salix Pharmaceutical (SLXP) , a new position, and which represented 3.4% of his portfolio at Dec. 31.

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3. David Tepper
Appaloosa Management
Portfolio Size: $4.04 billion

David Tepper bought shares of American Realty Capital (ARCP) , a new position, which accounted for 0.65% of his portfolio at Dec. 31.

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4. Leon Cooperman
Omega Advisors
Portfolio Size: $6 billion

Leon Cooperman bought shares of Tribune Media Co.(TRCO) - Get Report , a new position, which accounted for 2.9% of his portfolio at Dec. 31.

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5. Julian Robertson
Tiger Management
Portfolio Size: $510 million

Julian Robertson added positions of Apple(AAPL) - Get Report , which represented 6.65% of his portfolio at Dec. 31.

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6. Wilbur Ross
Invesco Private Capital
Portfolio Size: $866 million

Wilbur Ross bought shares of Xenon Pharmaceutical(XENE) - Get Report , a new position, and which represented 1% of his portfolio at Dec. 31.

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7. Daniel Loeb
Third Point LLC
Portfolio Size: $11.08 billion

Daniel Loeb added shares of Amgen (AMGN) - Get Report , which accounted for 13.4% of his portfolio at Dec. 31.

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8. Steve Mandel
Lone Pine Capital
Portfolio Size: $23.85 billion

Steve Mandel added shares of Priceline Group (PCLN) , which represented 3.2% of his portfolio at Dec. 31.


9. Bill Ackman
Pershing Square Capital Management
Portfolio Size: $16.04 billion

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Bill Ackman added shares of Zoetis (ZTS) - Get Report which made up 9.62% of his portfolio at Dec. 31.

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10. David Einhorn
Greenlight Capital
Portfolio Size: $7.52 billion

David Einhorn bought shares of Time Warner (TWX) , a new position, which represented 4.3% of his portfolio at Dec. 31.

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11. Eddie Lampert
RBS Partners (managed by ESL Investments)
Portfolio Size: $2.21 billion

Eddie Lampert bought shares of Sears Canada (SRSC) , a new position, which accounted for 12.2% of his portfolio at Dec. 31. (Lampert is also currently the chairman and CEO of U.S.-based Sears Holding (SHLD) . The Hoffman, Ill.-based company sold shares of Sears Canada last quarter to raise capital.)

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12. Carl Icahn
Icahn Capital Management
Portfolio Size: $31.9 billion

Carl Icahn added shares of Hertz Global(HTZ) - Get Report , which accounted for slightly over 1% of his portfolio at Dec. 31.

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13. George Soros
Soros Fund Management
Portfolio Size: $9.16 billion

George Soros bought shares of LyondellBasell Industries(LYB) - Get Report , a new position, which accounted for 2.5% of his portfolio at Dec. 31.

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14. Ray Dalio
Bridgewater Associates
Portfolio Size: $12.53 billion

Ray Dalio added shares of the Vanguard MSCI Emerging Markets ETF(VWO) - Get Report , which made up 1.7% of his portfolio at Dec. 31.

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15. Bruce Berkowitz
Fairholme Capital Management
Portfolio Size: $7.3 billion

Bruce Berkowitz bought shares of Sears Canada, a new position, which accounted for 1.9% of his portfolio at Dec. 31.

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