Mass Effect D6 by Lech

Mass Effect D6 system is made by Lech, and is compiled in a fairly comprehensive PDF at 138 pages with professional-level of layout. The latest version 2.35 was made in 2014.

Author's recommendation:

It may be helpful to download the D6 Space or the WEG Star Wars D6 rules, especially for space combat, this book differs somewhat from those standard D6 rules. This document will help you to GM and play in the MASS EFFECT setting. -Lech