I did the Machine Design & Materials depth.
I used the MERM, FE reference handbook, Shigley's Mechanical Engineering Design, the machinery's handbook, and a binder full of worked practice problems, notes, and pages from a few choice sections of college textbooks for areas I felt the MERM was lacking during the exam.
I also brought with me but did not open or remove from my crate the PPI Six Minute Solutions for mechanical systems, the latest (2016?) NCEES practice exam, PPI practice exam, MERM practice problems companion and mechanics of materials by R.C. Hibbeler. I did do all the problems in the six minute solutions, the two practice exams, and most of the MERM practice problems companion in preparation for the exam.