A weapon capable of killing angels. It does not look like a typical sword, but it appears to be somewhat of a blade. It is referred to as the Sword Of Lucifer in the official episode summary released by The CW, although it is never referred to as this in canon.
Uriel, a supporter of Lucifer is trying to recruit angels to his cause, which is to help free Lucifer from hell. When they refuse Uriel kills them with the Sword of Lucifer. Eventually Anna uses it to kill him.
As Zachariah tries to coerce Dean in agreeing to be the Archangel Michael's vessel, Castiel arrives, and attacks the angels with a blade which kills them. It appears to be the same balde used by Anna although this is unconfirmed.