Crude tactics can be effective nonetheless.

Barrage of Boulders

Barrage of Boulders deals 1 damage to each creature you don't control.
Ferocious — If you control a creature with power 4 or greater, creatures can't block this turn.

The List

Khans of Tarkir

Barrage of Boulders deals damage only to creatures you don’t control as it resolves. However, the ferocious ability affects all creatures, including ones you control and ones that weren’t on the battlefield as Barrage of Boulders resolved.

Ferocious abilities of instants and sorceries that don’t use the word “instead” will provide an additional effect if you control a creature with power 4 or greater as they resolve.

Some ferocious abilities that appear on instants and sorceries use the word “instead.” These spells have an upgraded effect if you control a creature with power 4 or greater as they resolve. For these, you only get the upgraded effect, not both effects.