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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I would like a thrower type weapon that changes function depending on the element. Solar would be a flamethrower, Arc a chain lighting gun, and Void a gravity thrower. The Gravity thrower would create a gravity distortion at a set distance and enemies would be sucked into it if within the blast radius. Then when you release the trigger or the gun runs out of charge the distortion explodes, the longer one holds the trigger the more damage that is dealt.