A great source for imperial one-liners is the "Imperial Infantryman's Uplifting Primer"
Just a few good ones from the bottom of the pages:
Honor the craft of death.
Ask not why, just do.
Thought begets heresy; heresy begets retribution!
Be strong in your ignorance.
A narrow view sees better.
Life is the Emperor's Currency; spend it well!
And the last 20 pages are nothing but prayers in His name. Quite inspirational to servants of the god-emperor, no doubt.