Trapped in drop pod glitch
From Halopedia, the Halo wiki
The glitch is triggered when the player stands beneath a landing orbital insertion pod, normally which would crush the player. If done as the enemies are exiting, however, the player will be sucked inside the pod, and be left there stuck inside. The pod's walls are protected by energy barriers, which allow the Covenant to exit but prevent the player from entering. This time, instead, they will now prevent him from exiting the pod, and the player will be unable to interact with the outside, or damage any enemies or players. Covenant will still respond to the player's presence, and will surround the pod, but be unable to harm them due to the pod blocking them off. After a period of time, the pod will be deleted from the map, and the player will be able to progress as normal. One could also try exiting by suicide, if by throwing a grenade at their feet, or firing a ricocheting weapon at the walls, such as a Sniper Rifle.