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
Gauss sabot guns as a heavys. (Rail guns)
Medium range
Incredible per shot damage to 1 target
All of them over penetrate targets
Holds 4-6 shots in a magazine.
Slow RoF (but faster then rocket launchers)
All 1 shot in crucible
[b]No AoE damage![/b]
aren't notoriously accurate.
Can adapt perks like firefly, explosive rounds and an extended version of headseeker.
You get about 10-14 shots in PvE but a heavy ammo on the ground only gives 3-5
Has a variable spool up time, but not as long as FR's, more of a hitch in the trigger for most.