Rocket launcher - This is the really hard choice in all honesty. Guass Gun Scope - Its useful, I original went for it first and then discovered siege mode, pass on this simply because siege mode does so much more damage for the ammo spent.
Combat shotgun 3 round burst is alright but for 3 shells you get the same damage you get for 1 shell with the explosive rounds Everything else is kind of just how you honestly use them.