Carl Icahn in Oct. 2007 (© Mark Lennihan-AP Photo)
Even at 77, activist investor Carl Icahn is a master at multitasking who shows no signs of slowing.

But he sure has hands full these days. Icahn is trying to persuade Michael Dell to abandon his $22.4 billion bid for the struggling computer company he founded and instead recapitalize Dell (DELL) and make a rich dividend payment to shareholders. Icahn has raised his investment in Herbalife (HLF), the multilevel marketer at center of his multibillion-dollar battle with a hedge fund titan. And he's blasting Transocean's (RIG) "ill-advised" mergers and has urged the offshore driller's board to raise its dividend.

What makes Icahn especially powerful lately is that he no longer manages money for clients, so he can do whatever he wants.Bloomberg estimates his fortune at $20 billion and notes that his investments gained 28% in 2012 and 35% in 2011.

Icahn has often gotten his way in the past, though that's no guarantee he'll continue to be successful.

The road ahead for Icahn at Dell, for instance, isn't easy. As The Wall Street Journal noted, the Round Rock, Texas, company needs just 42% of its outside shareholders to approve the founder's buyout. But so far, only 15% oppose the deal. Hewlett-Packard (HPQ) and Lenovo, the Chinese computer maker, both took a pass on joining efforts to defeat Michael Dell's offer, the newspaper says.

Herbalife pits Icahn against rival hedge fund billionaire Bill Ackman, who has made $1 billion bet that the seller of nutritional supplements and personal care products would fall. Icahn, who dislikes Ackman, invested in the company after Ackman described it as a "Ponzi scheme."

Icahn said he invested because he thought the stock was "cheap." Bloomberg notes that Icahn still feels that way and has raised his stake to 15.6% from 13.6%. Herbalife has agreed to add Icahn-backed members to its board.

And at Transocean, the company's board disagrees with Icahn's call for a larger dividend, saying it "would be overly aggressive and detrimental to the company's long-term performance," according to a company statement quoted by Reuters.

Shares of Dell, Herbalife and Transocean are up by double digits this year, thanks in part to Icahn. Investors need to remember, however, that the savvy activist's best interests may not coincide with theirs.

--Jonathan Berr does not own shares of the listed stocks. Follow him on Twitter @jdberr.

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