Square Enix has announced the first of many organized Conflict events for Final Fantasy XI, called "Ballista". 

Conflict is a new form of organized, non-lethal Player vs. Player features being introduced to give Final Fantasy XI extra flare to the citizens of Vana'diel (and preparation for a potentially disasterous event).

Here is an excerpt from the article:

This event is based upon a training exercise employed by the Royal Knights of San d'Oria. Competitors from each nation attempt to score the most points within a set time by throwing a stone, or "Petra," into a castle-like construction known as a "Rook."

After confirming the schedule for Ballista, competitors register their participation though the "Herald," the referee for the event. Once the competitors have all gathered at the appointed place, the Herald declares the beginning of the match. The first thing competitors must do is find a Petra, several of which have been buried somewhere in the playing field by the Herald prior to the match.

The interesting bits from Ballista is that sometimes it is necessary to kill an opposing team member to unlock a closed Rook.  Temporary abilities are granted during a game match such as faster movement speed for those lacking a Petra and a seeking ability for those with a Petra to find a Rook.  If a person was to compare it, they could compare it to modern-day rugby (except with a little more "umph" thrown in).

Square Enix promises to introduce more Conflict events in the future.

The full article, with some impressive in-game screenshots of Ballista, can be found here.