Disappearing Truth

The Disappearing Truth is a glitch that can be performed on Halo 3 campaign level The Covenant.

How To Do It
In the last section of the level The Covenant, after you have reached and killed the Prophet of Truth, you can melee (or "teabag") the Prophet of Truth once, causing him to fall through the platform on which his body rests. Note that the area in which Truth resides afterwords sort of resembles a tomb, a final resting place for the Prophet. When he falls beneath the platform you can see him, though you cannot reach him or get him out again. This also works on the Flood Combat Forms if you manage to kill them on the platform without destroying the body.

This is a glitch due to Halo 3's physics engine, and can be seen throughout the game if enemy, or friendly units, are killed in certain ways, or are moved to certain places using the melee attack. Another common glitch of the physics engine is when units are killed while falling, and stop, but their body keeps flailing about, like it is still falling.