Berkshire Hathaway is the company Warren Buffett calls his dumbest purchase ever.
It was a dying textile mill. In 1964 its boss agreed to buy out Buffett at $11.50 a share, then mailed paperwork for $11.375. Enraged by the chiseling, Buffett bought control instead and fired him. The grudge buy is now worth about $1.1 trillion, though Buffett reckons the spite cost him some $200 billion.
Berkshire Hathaway on Brandseum