yup! not discouraging anyone from contributing more stirring examples of pre-battle speeches, but FYI, there are several examples in the FAQ*
*see the popular questions link on the sidebar or the wiki tab above
One of Alexander's great gifts was his oratory. It was one of his keys to victory. His Greeks got real pumped up before battle and charged right into the most well defended part of the enemy line and break through their lines. Google: Alexander's speech at Issus.
And it carries on today. There's a youtube video I particularly like from the US Marine Corps before their advance into Marjah. I believe it was a Gunnery Sergeant from 1/6.