From May 6th to May 13th, Guild Wars 2 players can take part in a World Boss Beatdown event. Those taking part will be able to earn a Bonus Box of Goods for every one taken down. These can contain "especially shiny items like cosmetic infusions and invisible footwear". The community will be informed "when one of the loathsome creatures is active near you" in order to get groups together to "swoop in and smack it down".
Check out the details on the Guild Wars 2 site.