Unless you've been living under a rock, you know that the loudest voice to enter into the drama between Bill Ackman and his short, Herbalife is legendary investor Carl Icahn. Icahn has been working Wall Street since the 1960s, but it wasn't until the 1980s that he gained his reputation as a ruthless activist investor, taking a controlling interest in companies like TimeWarner, TWA, and Blockbuster.