You can use one weapon from the list directly below rules on top of the ones on the list as well as any non rare weapons or common drops you feel up to using for weapons
The above line is in the rules. Any non rare weapons you can use unlimited of. As long as the weapon that you use the majority of the time is the negative %s weapon you can use as many negative %s weapons as you want. Thats a good question for sure, thank you for bringing it to my attention. The weapon off the list is the list of weapons where you choose 1 rare weapon from to help you complete the list of tasks. As mentioned above the rare weapon you choose off the list can have any stats you see fit. I don't know how many realized that you can use any NON rare weapons you want. Again that is mentioned in the rules please keep in mind. So if you have charge vulcans 85 hit, a hell rifle with 65% hit etc etc...you can use unlimited number of NOn rare weapons. As well as whats specified in the rules/gear.
Let me be a little bit more clear so long as the negative %s weapons are non rare if your using more then one.