Custom game
From Halopedia, the Halo wiki
A Custom Game is a customizable gametype in all of the Halo games. To start customizing, you will first have to select Settings from the Main Menu. From there, you will choose from seven different game types. These include Slayer, Capture the Flag, Assault, King of the Hill, Oddball, Juggernaut, Infection, and Territories. After selecting your game type, you can then go and edit player options, vehicles, and weapons. You can customize things such as how much shielding players have(such as No Shields, Overshields, and regular shields), which vehicles appear/don't appear, as well as what weapons you can pick up during your game, the movement of the player, and much more. You can customize color in Halo CE, and in Halo 2 you can change the emblem and the character model, and in Halo 3 you can change different parts of the armor.
This can be done whether on local play, split-screen, or on XBox Live.
It is the same thing as "Splitscreen" from Halo 2 or "Custom Games" in Halo 3.
Psythik, a member of bungie.net, has made a online custom games finder, so if someone has no friends that are playing a custom game currently, they can find a game.
