[MegaBlues]

Any skill that performs a basic attack while using a gun would count.

Such as Cripple Arm/Leg, Parting Shot (I believe, don't quote me on this), Riposte, ETC.

Though, if you don't want to give them Skill scaling, they should at least get some other form of scaling. Only doing 20 damage on a critical hit is pathetic, and nowhere near 'it's a feature' territory.