Great ideas so far. I like st. Crispins day speech and Into The Breach as well. I'll put my two cents in. Everyone else can do the same and I guess we'll vote for it. 

There's Desperta Ferro!, which means Awake Iron (almogavor battle cry) - that can be something we all shout as we start our engines. 

Ride To The Sun! / Ride to Glory! - battle cry

Honor Me! - bit on ththe nose to Witness me, but can be shouted whenever someone does something badass to which those who witness it yell back Glory to the Road!