In Call of Duty: Black Ops II, it allows the player to equip an extra tactical grenade that takes up the lethal grenade slot, but it must be a tactical grenade of a different type.
Call of Duty: Advanced Warfare
"Take an Exo Ability in your Exo Launcher slot."
— Create-a-Class Description.
In Call of Duty: Advanced Warfare, it allows the player to equip another Exo Ability that takes up the Exo Launcher slot.
Call of Duty: Black Ops III
In Call of Duty: Black Ops III, Tactician allows to use another tactical grenade instead of a lethal grenade.
Call of Duty: Black Ops II
While Tactician is equipped, running out of the first tactical and attempting to throw it again with show a "Tacticals Empty" appear on the screen, but running out of tactical grenades in the lethal grenades slot will not show this message.