Lowering Weapon

In Halo 3 there is a way to lower your weapon in Campaign and in Custom Games (not Xbox Live). It is good for filming videos in theater.

Button Combo
To lower you weapon, press and hold the following buttons together:
 * RB
 * LB
 * Left Stick (Crouch)
 * Down on D-Pad
 * A

If done right, your weapon should disappear from your screen. Your character may also jump as a result of pressing "A".