This isn't one of the ideas in store that I mentioned earlier, but it did come to mind:
Name: Brigade Barrier
Weapon Replaced: Junk Shield
Colors: Yellow and Black
Description:
Brigade Barrier creates three small robot units around you that are static, but follow you everywhere until you call them off. When you get hit while this is activated, damage is halved and one of the robot units will fire a shot so fast that it can't be seen. Think of it as the same as having a Reflection Rune and an Armor in Skulltag at the same time. When called off, the robot units simply dissapear. Just remember that both activating this weapon and taking hits will deplete the ammo bar. You should be especially careful with ripping weapons, because even if your enemy will take damage too, the damage done to you isn't negated as well as other non-ripping weapons for obvious reasons. Getting up close to an enemy with this won't do damage, but it sure might discourage attacking.
As for how much ammo it has and how much is consumed when the barrier is activated or when you take a hit, that can be adjusted to balance things out. I have no idea how much it should have.