Get Infinite Spartan Laser Capability
When playing through the Halo Mission in "Halo 3," it is possible to get infinite ammunition for the Spartan Laser. Continue through the level until the encounter with Sergeant Johnson. Shoot him using friendly fire until he falls and drops the Spartan Laser. Pick up the weapon and continue to shoot Sergeant Johnson until he is forced to kill your character. After your character respawns, knock down Sergeant Johnson a second time and pick up the Spartan Laser he drops again. Sergeant Johnson should rise and have another laser across his back. Shoot him down a third time and pick up the gun he drops. This weapon will have infinite ammunition.
Rapid Spartan Laser Fire
To acquire a rapid laser fire mode for the Spartan Laser, enter Forge mode and equip a Spartan Laser. Charge the laser until it is just about to fire and then switch back to Monitor mode. Move around in Monitor mode until you select a suitable target and hold the right trigger button before returning back to the avatar. When back in Player Control mode, the Spartan laser will fire almost instantaneously.
Unlocking Weapons and Armor
You can unlock various weapons and armor during the course of "Halo 3." To unlock the Katana sword, complete all 1,000 achievements in the game and find all the Skulls. To get the Mythic Armor, which comes with the Mythic Map Pack DLC, acquire the three Vid Master Challenge achievements.
Additional Cheat Tips
"Halo 3" has three alternate endings. Its first ending occurs when you complete the Easy, Normal and Heroic difficulty settings. You can access the second alternate ending by completing the game on the Legendary difficulty setting. View the third ending by completing the game on Legendary and acquiring all of the Skulls. To make Legendary difficulty easier, activate an idle second player, which will respawn rather than restart after dying.