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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SMG Grenade Launcher Plasma based weapons (but I guess Fusion Rifles count as one, but never hurt to ask) Actual Side-arms (dont get me wrong I love those Mancannons reminds me of Vash the Stampedes weapon)