Legendary items are extremely powerful, named items which were wielded by characters of lore before. Examples of these are:
- Ashbringer (a sword forged as the ultimate holy weapon),
- Atiesh Greatstaff of the Guardian wielded by Medivh,
- The Warglaives of Azzinoth, wrested from the hands of Illidan,
- Val'anyr, Hammer of Ancient Kings,
- Sulfuras, Hand of Ragnaros,
- Peep's Whistle, summoning Kael'thas' phoenix mount,
- Shadowmourne, the most dangerous axe in Northrend,
- Thori'dal, the Star's Fury, a legendary bow.
See the related link for a full list of all items classified as Legendary in World of Warcraft. Note that some of these are only usable as part of a quest or encounter, and that your character cannot keep it.