probably some “proprietary trading” firm, large blue chip companies for example generally “invest” in things other than securities, such as expanding the business, but dont get me wrong they do, but their main business is not securities trading. A propriety trading firm almost always private so there really is know way of knowing, off of the tip of my tongue i cant even think of any publicly held prop trading companys. You might want to try looking up a hedge fund that is publicly held such as Och-Ziff Capital i THINK their ticker is OZ

The best traders on the planet work for Goldman Sachs, ticker GS. I don’t believe, however, that any company releases information on how much money their trading desks have made or lost. It’s just all rolled in with company profit.

Biggest loser is probably Lehman Brothers, LEH, or Citigroup, C.