here's one: Specialised Munitions Racks: _____ (insert Energy, High Explosive, Kinetic or Fragmentation here). It transforms all ballistic or ammo-using weapons on the ship to that ammo type, with a small percentage penalty to hull strength and a decreased ammo capacity for all weapons.
benefits: a high degree of specialisation for your ships is available
drawbacks: highly specialised ships
This is probably most useful for endgame fleets, where creating dedicated task groups can be easier by making a hound covered in MGs deal stupid amounts of HE damage to overloaded capitals, while being screened by your own larger ships' PD systems.