Ares' Sword

Ares' Sword is Ares' symbol of power.

Appearance
Oddly, Ares' symbol of power in myths was a spear while it is a sword in the series. In the modern era, it is usually disguised as an aluminum baseball bat. Ares can morph the sword into whatever weapon he wants.

The Lightning Thief
In The Lightning Thief, Ares originally disguises it as an aluminum baseball bat before he uses it as a two-handed sword against Percy in a duel at a beach in Los Angeles. Additionally, he disguised it as a hunting knife. Disguised by the Mist, it appeared to be a shotgun to mortals.