Grenade animation glitch
From Halopedia, the Halo wiki
On any level with Infection Forms and Grenadesin Halo PC , a strange glitch is possible to perform. Basically, when the Flood Infections are draining your 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 models completes the animation (and the throw!) of the grenade being thrown. I'm not certain if this works on Xbox, so if someone would try it out please and come back and share that would be great!