Not sure if anyone else has posted this one but...
For "Scarecrow"... In Act 5 Chapter 3 after the building and sewer you'll enter a large courtyard. First, clear the area of all but one enemy. The all you have to do is kick a Nom Parasite onto him then manoeuvre him so that a kik will net you the "Pricked" skillshot.
As long as the Nom Parasite is still on him you'll get Scarecrow.