A "Devils Arm" from the Devil May Cry franchise from the first Devil May Cry. It is a sword of demonic power, activating a lightning based demon form in Dante.
Devil May Cry
On his way through Mallet Island, Dante comes across Alastor. In order to prove he is worthy of using Alastor in battle, Dante must show his demonic abilities. Alastor does this by impaling Dante into the ground. In typical fashion, Dante arises through the sword, taking it for himself and adding it to his collection of Devil Arms. Alastor doesn't feature in the series afterwards, the various Devil Arms Dante finds in the series always take a backseat to swords owned by Sparda.
The spirit of the Alastor sword manifests as the boss, Alastor, in the Viewtiful Joe series.
Alastor is unique in the series as it is lightning based. This proves useful against a lot of foes in the game, less so against some electrical enemies. The elemental qualities of the first game doesn't feature heavily in the sequels due to some weapons having elemental affinities but doing the same damage to all enemies, whereas some weapons are copies of Devil Arms from DMC1. It's also the first weapon in the first game to activate Dante's Devil Gene, giving him access to the Devil Trigger. It changes Dante's DT form into a lightning based demon, capable of firing electric-powered bullets, significantly increased speed and flight in which Dante fires thunderbolts from his hands.
It's movelist is mainly the same as the Force Edge but with additions that the Force Edge catches up on when it becomes the Sparda Sword.