Final Grunt

The Final Grunt is found cowering on the edge of a cliff right before the Forward Unto Dawn section on the final level in Halo 3. If the player approaches him, he will repond with "Hey demon! The jerk store called and they're all outta ya. Poor demon kidnapped at the age of six and conscripted into the military. Hey, if you let me live I'll give you the Fist of Rukt, I'll even be the bottom. I'll polish your boots, I'll polish your helmet. Its the gas; I don't know what I'd do without it.

However, discovering the "Final Grunt" leaves the player unable to complete the end of the level (and the game), because there will be no route to the end since the platforms will have fallen.