Folder: If my long weapon is an M4/AR15/M16, well, Leatherman sells a multi-tool that has specific tools for the weapon system. This might get the nod, as my folder.
Fixed-blade: Spartan Blades Les George V-14, a 21st-Century interpretation of a couple of WW2 daggers.
Much as I would have liked to have named a Bowie or other chopper-capable knife, a gimpy shoulder has relegated me to blades more-suited to point-driven techniques. If I am going to wield a big contact weapon with my “other” arm, I would rather it be an axe/hatchet/‘hawk. As a fan of Bowies, it is not easy for me to say this, but it is what it is. The above-mentioned dagger, at just under 7” in blade length, and slim, is the largest knife that I can use right-handed, effectively.