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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Something like the Quake 3 railgun, as a sniper alternative (high-impact, overpenetrating, hitscan weapon with a tiny firing delay and deceptively slow shot trail that gives away your position, and slow reload.) A shotgun that fires a single slug with huge range, only it's a baton round (only lethal to weak mobs, otherwise just pushes enemies back and heavily staggers them with minor damage.)