Event items are collectible goods, such as Dwarven Relics, Sparkfly Essence, and other such materials needed to complete certain Dynamic Events. Most commonly, an NPC will request from the players in the area to collect certain items within a clearly marked geographical location on the map, and bring them back to them. Once the NPC has collected enough items, they will generally run back and make something with them, such as a new bundle, food or other item, and offer the item for sale. The resultant product is generally only available for sale for a few minutes after the event ends. Included within this category are Legendary collectible items, usually provided after completing a specific event(s) within a clearly marked geographic area. These items have NO intrinsic value (outside of the collection itself), cannot be sold or salvaged, and are account-based (which means that as long as the Legendary weapon/armor collection is active on the account, ANY character can obtain the collectible). To avoid clutter, these items can safely be destroyed (but first ensure they have been "acquired" within the collection).
Except as listed, most event items very rarely have any value outside the event, or can be sold for merely 1 copper, so they can be destroyed or sold if possible without consequence.