The Odd Flood Glitch is a glitch that can be performed on any level with Infection Forms and grenades in Halo PC and Halo: Combat Evolved.
Walkthrough
When the Flood Infection Forms are draining your health bars (i.e. when your shield is down), right before you die, throw a grenade. The camera will behave just like you died, but your body model completes the animation of the grenade being thrown.