15. Oracle Buys ATG

Sale Price: $1 billion
Year: 2010

You probably wouldn't know ATG, or Art Technology Group, by name, but more than likely you've seen their work: the eCommerce software firm built the online stores of giants like BestBuy and Tommy Hilfiger. In 2010, the veteran systems giant Oracle handed over $1 billion in order to bring ATG and its customers into the fold.