Some of the rules for the Halo 3 game modes can be confusing and there are some guidelines I'd like people to follow that can't be explained through Halo. I'm going to explain each game mode and some rules to go along with it. Hopefully this clears some things up.
Slayer
Name: Slayer
Author: Bungie
Description: Free For All. 25 kills to win.
Weapon(s): Assault Rifle
Rounds: 1
Other: N/A
Name: Team Slayer
Author: Bungie
Description: Form teams to take out the enemy. 50 kills to win.
Weapon(s): Assault Rifle
Rounds: 1
Other: N/A
Name: Rockets
Author: Bungie
Description: Free For All with Rockets. 25 kills to win.
Weapons(s): Rocket Launcher
Rounds: 1
Other: No other weapons on map
Name: Eliminatio
Author: Bungie
Description: Highly tactical Team Slayer. 5 kills to win.
Weapons(s): Assault Rifle
Rounds: 5
Other: Time Limit - 3 minutes
Name: Duel
Author: Bungie
Description: Free For All but no camping! The leader has a waypoint over them. 10 kills to win.
Weapon(s): Assault Rifle
Rounds: 1
Other: N/A
Name: Spartan Joust
Author: TIGERSHARK27
Description: You may only attack enemies and be attacked by an enemy while on a vehicle.
Weapon(s): Spartan Laser
Rounds: 1
Other: Infinite Ammo, Motion Tracker only tracks Allies
Name: Team SWAT
Author:
Description: Team Slayer with no shields. 50 kills to win.
Weapon(s): Battle Rifle, Magnum
Rounds: 1
Other: 12 minute time limit, Mongooses only are available for use, 150% Damage Resistance, no shields, no grenades, Infinite Ammo, no motion tracker
Name: Sacrifice
Author: Predator5791
Description: Made for 'Lava Pit'. Knock your opponents off the edge and be the last man alive to win the round. Other Joust rules apply except splattering.
Weapon(s): Magnum
Rounds: 10
Other: FFA, no score limit, Indestructible vehicles, 2 minute time limit, 200% Damage Resistance, Enemies cannot give damage, no grenades, 50% Player Speed (slower), 150% Gravity (heavier), no motion sensors
Name: CoD
Author: B0Oth
Description: Free for all and instant kills. 50 kills to win.
Weapon(s): Magnum
Rounds: 1
Other: Each shot is an instant kill, Infinite Ammo, 75% Speed, 200% Gravity, no vehicle use, no motion tracker, Motion trackers only senses allies, Forced color is black (for your character)
Name: Soccer
Author: TIGERSHARK27
Description: It's pretty simple, just try to hit the soccer ball into the opposing net. You'll have to keep score yourself and assassinations aren't allowed.
Weapon(s): Gravity Hammer
Rounds: 2
Other: 8 minute time limit, no weapons on map, no grenades, no vehicles, Custom Powerups, Invulnerable shields, Infinite ammo, 125% Speed, Motion tracker range increased to 150 meters