In Dead Island Riptide, a new group fury option has been introduced. It is unlocked by putting at least one point in the appropriate skill in the middle of the Fury skill tree. Group fury is activated by pressing the Fury button again before hitting anything in Fury.
Some Fury skills affect you while you're in Fury, but it is unclear whether or not that they still apply if one activates group fury. Do fury effects work during group fury?