2014 Change: 55%

Market cap: $47.8 billion

Major holders at Sept. 30: Vanguard Group (4.90%), Fidelity Management and Research (4.33%), State Street (4.03%), Artisan Partners (3.21%), BlackRock Fund Advisors (3.07%), Grantham, Mayo, Van Otterloo (2.87%), Paulson (2.79%), Wellington Management (2.77%)

Why is it up? Covidien ($COV) told investors that 2014 would be a transitional year, and the company delivered on its promise. In January, the Irish devicemaker boosted its Q1 revenue by 3% to $2.6 billion, setting the stage for future growth. In March, the company charted a milestone when stock hit a 52-week high, reflecting shareholder contentment in recent product launches and acquisitions including Covidien's $860 million purchase of endoscopic pill maker Given Imaging. But the icing on the cake came in June, when the company announced that it would merge with med tech giant Medtronic ($MDT) in a $42.9 billion deal. The deal price represented a 33% premium to Covidien's June 13 close, and Covidien shareholders will own about 30% of the combined company as a result of the merger. Shares continued to reach new highs after the deal was announced, closing at $101.66 in late November--a one-year return of around 48%, Zacks analysts noted. The same month, Covidien agreed to sell its drug-coated angioplasty balloon to Spectranetics ($SPNC) for $30 million to usher its deal with Medtronic past U.S. regulators.

What comes next? Covidien and Medtronic recently won shareholder support for their pending merger, clearing the deal of most of its final obstacles. Zacks analysts see the company poised for more growth in 2015, as Medtronic's takeover is expected to generate significant synergies moving forward. The merger is expected to result in at least $850 million of annual pretax cost synergies by the end of fiscal year 2018. But Covidien still "faces stiff competition and remains exposed to pricing and utilization in certain end-markets," Zacks analysts note.

COV Chart

COV data by YCharts

For more:
Medtronic and Covidien win shareholder approval for proposed $43B merger
Covidien acquisition of Reverse Medical illustrates vascular device focus
Covidien is popping the bubbly for positive Q3 numbers
Medtronic merger could give Covidien execs an $80M payout
Medtronic gains better hospital access with Covidien purchase
Covidien CFO deals his stock options near the company's 52-week high
Revenue ticks up as Covidien braces for transition

-- Emily Wasserman (email | Twitter)