The Time Feather
It looked like the Mastermune from Chrono Cross
+25 acidic blast fiery blast icy blast lightning blast sonic blast keen vorpal everdancing two-bladed sword
- as a free action, it can turn into any other weapon (axes, whips, spears, etc...) or shield
- as an immediate action, can provide the bearer with immunity to any single energy type
- was sentient
- against deities, it could penetrate their damage reduction, always did critical damage, and on a critical hit could kill deities.
It was previously a sword known as the Avatar-Killer, but my player recovered it, reforged it into a weapon she could use, and became one of the deities' most feared beings in the Multiverse. She eventually ascended to become the head of the pantheon of deities
It had a host of other other spells that could be cast, but my player never used them and we kind of forgot about them.
My favourite epic game.