My [Dethcube Prime] is mainly used for generating energy for the warframe its equipped on.
The Energy Generator mod (from Simaris) makes [Dethcube Prime] drops energy orbs when wen it has assisted in a certain number of kills.

I tend to equip a hign fire rate weapon on [Dethcube Prime] so he assists with a lot of kills and you get lots of energy orbs.

Vigilante Deth Machine Rifle Prime build here. Gives a 20% chance for enhancing critical hits on Primary weapon.
Fast fire rate Deth Machine Rifle Prime build is here.

Any warframe you struggle to manage your energy try [Dethcube Prime] and the fast fire rate [Deth Machine Rifle]