If the mob attacks by thrusting a dagger straight outwards in the direction they're facing, you can do something like this to find the targets:
for(var/mob/m in front(8, 12, 13))
The bounding box extends 8 pixels in front of your mob, it's bottom is at the 12th pixel of your icon and the top is at the 13th pixel.
The other change is that step_x and step_y are used in the atom's New() proc (if the atom is an /atom/movable) to set the object's initial px and py vars. This lets you define static pixel offsets for all objects - previously you'd have to do this in their constructor:
// you used to have to do this:
While these changes are useful, they were added mostly for the Sidescroller Challenges. I just added three more challenges, two of which are made easier by these changes.