[Soul_Hacker]

You can use Cripple Leg without a gun equipped, wherein it will let you target an enemy, show the hit/crit/damage chances, and upon confirmation. . .

Eat your momentum with no effect.

I figured it might be a bug, considering generally you just can't use skills if you have an improper weapon equipped.

Weapon I was using was a pair of boxing gloves.

[Snake]

You found out the boxing gloves special feature, which allows you to fingergun taunt kill someone's legs off.

Are you sure you're just not doing the quick time event right?

(this a joke)

[Neus]

This should be corrected in 2.81.