Put Down Weapon

Put Down Weapon is a trick that can be done in Halo 2 and Halo 3. This trick causes the player’s weapon to disappear from the player’s screen (in Halo 3) and if the weapon is a rifle of any kind, then it will be “put down” from another’s perspective.

Halo 2
To perform the trick, just simply press “down” on the D-pad or exhaust all available grenades and hold L (only on Xbox Live). NOTE: It will not be shown on the player’s screen but will be seen by others. Shooting, throwing grenades, meleeing, reloading, entering vehicles, dying, or just pressing “down” again will cause the weapon to pop back up.

Halo 3
Press and hold LB, RB, A, crouch, and “down” on the D-pad for 3 seconds. This time, shooting, throwing grenades, meleeing, reloading, picking up support weapons, going into edit-mode on Forge, entering vehicles, or dying will cause the weapon to pop back up.

Trivia

 * This technique has been used in many machinima like "Red vs Blue" or "The Codex" to make the characters appear to be in conversational, rather than combat-ready, mode.
 * In Halo 3, this trick has many special properties (see Silhouette Sword).
 * In Halo 3 Split-Screen, this trick may be a possible method to combat Screen Watching.