The Missing Androids of Halo
I've read literally every book, and played every Halo game in existence and only recently noticed the complete absence of Androids, Robots and all other manner of automatons. Humanity has AI technology capable of the most complex calculations, capable of simulating personalities. In Halo 4 we see a weaponised exoskeleton. So how hard can it be, to put the two together (Mjölnir)? In the end Halo is a story about the Master Chief and even more about his remarkable luck, but this complete neglect of a classic sci fi concept is strange.
_PS. Guilty spark is a Forerunner construct, it doesn't explain humanity's myopia in this subject._