The gun that comes with the terminus armor from gamestop, is that a heavy weapon or an assault rifle? :q
And what kind of gun do you get with the inferno armor?
Blackstorm is a grav gun heavy weapon, very good crowd control my second favorite heavy gun.
But I don't want to use a heavy weapon. I'm an Infiltrator, I don't want a huge block on my back. They will have to fix this.
Then just carry the flamethrower and dont use it, always nice to have the choice, or use the avalanche, freeze people then shoot em.
I used the Missile Launcher with my Infiltrator, accurate and deadly, just as she is

For my vanguard it's the flamethrower, and my soldier never upgrades from the grenade launcher. Flamethrower is the smallest of heavy weapons, but the ML isn't that big either.
I dont know about you but for me it was utter crap, missiles went off to the sides and on a mission collecting crates blew them up, even when aimed in the middle they still went to the side, accuracy is a problem for it.