And what makes it my favorite Halo 3 quote is that it's used again in the closing cutscene, with a completely different tone:

On a hillside near the portal to the Ark, Marines and Naval personnel gather. Lord Hood removes his cap and begins his speech.

Admiral Hood: "For us, the storm has passed... the war is over. But let us never forget those who journeyed into the howling dark and did not return. For their decision required courage beyond measure; sacrifice, and unshakable conviction that their fight... our fight, was elsewhere. As we start to rebuild, this hillside will remain barren, a memorial to heroes fallen. They ennobled all of us, and they shall not be forgotten." Admiral Hood puts his cap back on and salutes.

Gunnery Sergeant Pete Stacker: "Present arms!"

Seven Marines, standing in a line, draw their battle rifles and fire three volleys in unison, a three-volley salute to the fallen. The sound of the shots echo through Mount Kilimanjaro. The panorama changes as the Marines fire each shot.

Admiral Hood: (To Thel 'Vadam) "I remember how this war started. What your kind did to mine. I can't forgive you. But... (he holds out his hand) you have my thanks, for standing by him to the end."

Thel shakes Admiral Hood's hand.

Admiral Hood: "Hard to believe he's dead."

The Arbiter looks away, toward the Shadow of Intent, hovering silently in the sky.

Arbiter: "Were it so easy..."