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
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Grenade Launcher, either traditional or an air-burst variant to remove enemies hiding behind cover. Would have to be limited to avoid over-reliance. Team support weapons: Offensive- Mortars that would provide for indirect fire. They could only be used in certain locations (because launching an explosive shell inside a building is a terrible idea) & would require a teammate to be the one to call it in. Defensive- Energy Shield that a player could pop up that would create a shield over all team members. It would block X amount of damage & once activated would drain your super charge by 50%. It produces no orbs so it can't be stacked or used to build other supers, it's sole purpose is survivability. Mechs- Right now we're the last remaining antpile in the known universe & for some reason no one wants to just commit to squashing us but if they did, we're shit out of luck. Having mechs would allow us to defend an area with less Guardians in one spot so we can defend the City adequately. Would work best in a mission where we're trying to repel an assault on a valuable location.