Be creative here there are no wrong ideas.
I would like the Spartan laser to be a weapon personally, just called something different "Charge Rifle" was a name I had in mind
-
Hunting shotguns: low ROF and stability high accuracy and impact with slug rounds. Heavy weapon slot satchel charges or command detonated explosives. continuous beam weapon low damage to start massive damage and weapon overheat at the end. Emp weapon perk, or heavy causes loss of radar and static vision. Gravity gun: loss of jumping or second jump slows agility. Freeze ray or projectiles: continued hits cause slowing then freezing shattering for a kill.