Grenade launchers, Spartan Laser type heavy lasers, flamethrowers? Crossbows? Idk maybe something like the Torque Bow from Gears. SMG somehow? Maybe as primary, but it's not really needed. Railguns? There's not much other gun types not in the game already really so idk. I think we will highly likely get Grenade launchers as a new heavy tho, either that or a spartan laser type gun.