If you want kickass pure and simple, go with somthing Patton said.
http://military-quotes.com/Patton.htm
If you want thought provoking, go with somthing Biblical
If you want thought provoking and controversial, go with somthing a Dictator said.
I had one of these things at the end of Middle School a few years back. I remember I used Isaiah 6:8, which is often used In a military sense.