Bungie published an interview on its website with their Design Producer Curtis Creamer:
Q: Without ruining anything surprising or too secretive, describe one of your favorite moments from Halo 3’s Campaign:
CC: My favorite moment has to be playing through one of the missions with what we call a “death blossom”. One of the cool things you can do in Halo is switch weapons with your marine allies. So, we’ve got this new version of the Warthog, the troop carrier, that can carry you and 4 other marines. As I’m playing through, I’m picking up every Fuel Rod Cannon I can, and I’m giving it to my marine buddies. Then I’m driving this warthog with 4 Fuel Rod Cannon marines on board (the “death blossom”), and we go rolling into an encounter against a bunch of Brute Choppers and Wraiths. Explosions and hilarity ensued! The capper was that mission designer Chris Opdahl had just made it so that a couple of Brute Choppers would join the fight by launching themselves off the side of a bridge and into the encounter. I didn’t know that he’d done that, and I go driving under the bridge just as one is coming down. It landed on my head blew the crap out of me and my marines. I laughed so hard, snot came out of my nose.
Oh, and the ending. OMG. I cried a little. Seriously. In a good way, not in a Halo 2 way.