Energy sword
From Halopedia, the Halo wiki
File:Energysword.jpg
Energy Sword
The Energy Sword is carried by high-ranking Elites. They have similiar ceremonial functions as swords in today's modern armies. While not often used in combat they do provide a good last ditch weapon.
The blade itself seems to generate plasma energy in a similiar way as the Covenant plasma weapons. In a plasma gun the energy is shot out like a bullet, but the energy from the sword is held into a blade-like form with small magnetic field generators built into the handle mechanism.
If the wielder drops the weapon a fail-safe activates and deactivates the magnetic field without first dispensing the plasma consuming the handle thus destroying the weapon.
