Earlier in May we discussed the Group Pose utility (more commonly known as GPose) at length in Echoes of Eorzea, and went through all the features available at that time, with a very brief look at upcoming additions.
Modding is a difficult process sometimes. Anamnesis is a standalone tool that is used to modify certain clientside-only values and allow the user a greater degree of flexibility for making creative and interesting screenshots. It removes the game's overbearing UI, presenting me with a series of filters, lighting options, poses, and camera angles.
It is a beautiful story about innocence, love, and appreciating the little things. Chances are you gave the game an invalid value for either Main or Offhand weapon in the equipment tab.