The Energy Sword deals very high damage per hit, on par with fully-upgraded Baseball Bat and Tentacle Bat , and desintegrates killed enemies as well as objects and car parts. Once upgraded with side quests, killed enemies drop larger amounts of health, making it a good melee weapon to go berserk and decimate enemies at close range (while bats, who have a greater knockback effect, are better to keep strong enemies away while overkilling weaker ones anyway).
The Laser Razor is the only costume for the Energy Sword in the base game. An additional costume, the Braver Sword, is available in the Anime Pack DLC.
There are no upgrades for the Energy Sword, and no "ultimate upgrade". However finishing Asha's side quests increases the amount of health dropped by enemies killed with this weapon, and can be seen as a free and unlockable "ultimate upgrade".
The blue-coloured 'Cool Blade' skin and the description "The hero's choice" are references to the blue lightsabers used mostly by good characters is the series, such as Obi-Wan Kenobi.
The red-coloured 'Hot Blade' skin and the description "Zinyak's favorite color" are references to the red lightsabers used mostly by antagonistic characters in the series, such as Darth Vader.
The Green Blade skin and the description "Because, you know, we already did red and blue" reference the third colour of lightsaber used in the original trilogy, used by Luke Skywalker in Return of the Jedi.
As purple is the signature color of the Saints, the Default skin may not be intended as direct reference to Star Wars, although a purple Lightsaber is used by the character Mace Windu.
The Energy Sword was first revealed in the Gamespot gameplay video.
The Brady strategy guide does not list the Green Blade skin.
The 'Braver Sword' skin, along with the matching Shonen costume, are both references to Final Fantasy VII's protagonist, Cloud Strife, while the description of this skin refers to the fact that such sword is absurdly large as it would have a weight of roughly 100 kg.