Yogg-Saron drops Tier 8 Chestguard tokens for all classes. In addition, he drops powerful weapons and armor, some of them from Warcraft lore. ilvl219 and ilvl226-232 pieces drop on 10man and 25man respectively.
When defeated in the hardest two modes of difficulty, Yogg-Saron will drop additional loot. Defeating him on 10man with One watcher assisting gives i226 or i232 loot. Defeating him with Zero watchers assisting yields a unique trinket known as Vanquished Clutches of Yogg-Saron.
On 25man, Yogg-Saron will drop i239 loot if One watcher is assisting. If defeated for the first time in the server's history with no watchers helping, players are given a one-time title called "(Name), Death's Demise". He also drops Mimiron's Head, a 310% speed mount.