The Fist is a social club much like the French Revolution, Black Panthers, or Communism. It first rose up when Dwight became acting manager. Known members include, Jim Halpert, and possibly Darryl Philbin. Dwight once attempted to join The Fist but was not accepted because of bad timing due to Operation Overthrow. Unbeknownst to Dwight, simply raising a return Fist when challenged with a Fist qualifies one for potential membership (much like a secret handshake).
The Fist is not a rebellion, although constantly mistaken for one.