Legendary investor Warren Buffett lost his leading heir apparent at Berkshire Hathaway on Wednesday, when his favored lieutenant David Sokol resigned.

Sokol, who was chairman of MidAmerican Energy and NetJets, resigned after buying shares in a company that he repeatedly pushed Buffett to buy. Here are some other Berkshire executives seen as possible successors to Buffett:

• Ajit Jain, Berkshire Hathaway: Reinsurance Group chief Jain, a Berkshire veteran, has been repeatedly praised by Buffett for his running of the insurance business, which has grown from "a standing start in 1985" to one "with float of $30 billion and significant underwriting profits."

On a recent visit to India, Buffett skirted questions on his succession plan but praised Jain.

"He loves what he does, he's not looking to take my job. If he was, the board of directors would probably put him in there in a minute," Buffett said.

• Gregory Abel, MidAmerican Energy Holdings CEO: Buffett has repeatedly called Abel a "terrific manager" and part of a "dream team" at the Berkshire-owned utility, which also included Sokol. In his annual letter to shareholders, Buffett praised both Sokol and Abel for "outstanding results." The utility's profits rose 7% to $1.2 billion in 2010.

• Matthew Rose, Burlington Northern CEO: Rose joined Berkshire after selling the No. 2 U.S. railroad company to Buffett last year for $26.4 billion, and recently made it to a Vanity Fair magazine list of top four candidates to succeed Buffett. Burlington Northern's profit rose 43% to $2.5 billion in 2010, and Rose was praised by Buffett in the annual letter.