Dropping wire from attic through existing interior drywall wall
Since this cable is going through a concealed space between access points and adding support is impracticable, NEC 334.30(B) applies:


  (B) Unsupported Cables. Nonmetallic-sheathed cable shall
  be permitted to be unsupported where the cable:
  
  (1) Is fished between access points through concealed
  spaces in finished buildings or structures and supporting is impracticable.
  
  (2) Is not more than 1.4 m (4&half; ft) from the last point of
  cable support to the point of connection to a luminaire
  or other piece of electrical equipment and the cable and
  point of connection are within an accessible ceiling.


So, go ahead and use NM if you wish.  (The NEC has equivalent wording in 330.30(D) for MC cable and 320.30(D) for AC cable, BTW.)