The Assailant Class Frigate is a ship class for the purpose of Infiltrating enemy territory, gathering information, and striking and vanishing.
The Eradicator class Cruiser is a ship class for the purpose of using its bombardment cannons to destroy the enemies of the Imperium before they even know what hit them.
The Retaliation Class Cruiser is a ship class for the purpose of bombarding heretical positions from orbit with both magma bombs and bombardment cannon.
The Espionage class Cruiser is a ship class for the purpose of dispatching agents to worlds via Thunderhawks stealthily for the purpose of sending teams to end corruption before it has a chance to spread.
Assassin Type Stealth Field Generator: Acting through the Void-shield the ship will remain in cloaked until the void-shield hit at which point the field will collapse and will only come back online once the shield(s) have recharged.
Disclaimer: this model is completely unofficial and in no way endorsed by Games Workshop.