The Falx

[Donciorate]

I think that the falx would have the capability to cut a scutum and through flesh if not more. It is the simple idea of a lever, the longer the arm reaches out from the fulcrum which in this case is the hands the more force can be exerted through it. That would seem to be the main purpose of putting the blade on a shaft in the first place.
The falx also has another advantage in its size, when you swing a blade downward you have a limited amount of time to bring the weapon up to speed. With a falx you raise the weapon up another 4 feet and that gives you more time to bring the weapon up to speed further increasing the speed and power of the weapon.
The Celts were known to have used weapons much like tools, raising there swords above their heads and bringing them down like they were cutting wood. This originated in the belief that if you can generate enough force with an instrument coming downward to cut a log, then you can do it with enough force to cut a human. So you take that same principal and add more length and more weight and you get a simple analogy of the person and scutum are the log, and the falx is a very big axe swinging from very high up.
As a soldier I have specialized myself in axe combat, the axe like the falx has its advantages in the fact that all the weight of the weapon is in the head which is far from the body giving it more force in the swing.
I definitely think that the falx is easily one of the more powerful weapons in anti-Roman arsenal.