Phantom Flood whip

The Phantom Flood Whip is a glitch on Halo: Combat Evolved that can be done on any level that includes the Flood.

Walkthrough
In order to see this glitch, play through the level until you see a Flood Combat Form, then approach until it starts a melee attack. As the arm swings back, shoot off the arm/whip it would use. Although the arm whip is gone, you can still be damaged as though it was still there. This is a difficult trick to pull off, as the attack is usually quick, but with quick timing and good aim, you will be able to do it.