Anti-material and Anti-tank rifles spring to mind.
Remember, the weapons in the Fallout world evolved to deal with an armored foe, so something like a Barret Light Fifty would be an ideal solution. Mortars might also be considered "big guns", and, while you can easily pack a mortar around I'm not sure how often you'd find employment for it.
Remember, the weapons in the Fallout world evolved to deal with an armored foe, so something like a Barret Light Fifty would be an ideal solution. Mortars might also be considered "big guns", and, while you can easily pack a mortar around I'm not sure how often you'd find employment for it.