My favorite moments will always be in the Halo 3 custom games/forge. I remember just hanging out with a few of my buddies screwing around with the gravity and speed settings and turning them into infection gametypes on sandtrap. Or even just screwing around playing lone wolves where the leader gets overshields and a gravity hammer. I thought I was so pro as I had been playing Halo for years. Then I took to the multiplayer for the first time on XBL and got put in my place. Good times. (Picture isn't mine, but that is still one of my favorite gametypes.)