They already have promethean vision.
Forerunner:
Charger: It would resemble a crossbow, and would charge up (Like the Railgun) and shoot an explosive crossbow bolt that would explode on impact.
Launcher: It would shoot a bouncable explosive and explode 2 seconds after impact. It would have a spreading explosion, shooting Scattershot type bullets, 360 degrees.
Hardlight Ax: It would be like a cross between the Grav. Hammer and the Energy Sword. It would have a Hardlight blade and would look kinda like this: http://www.aceros-de-hispania.com/image/battle-ready-sword/150-battle-axe.JPG
Beam Turret: It would be like the Sentinel Beam but look more Promethean-like and act like the Machinegun Turret(UNSC).
Covenant:
Thunder Rifle: A Covenant shotgun type thing, it would shoot 4 plasma pistol shots and to as much damage as the Shotgun but have slower moving shots and a little shorter range.
Sticky Launcher: it would be almost exactly like the Plasma Launcher from Reach, but would just shoot one faster moving grenade.
UNSC:
Avenger: A fully automatic shotgun with low damage but high fire-rate. (Futuristic AA12)
