Outskirts Energy Sword
From Halopedia, the Halo wiki
To reach the sword, one must get to the Outskirts vacation; this can be accomplished at the very start of the level. As soon as you exit the room with the crashed Pelican, jump onto the door frame. From there, jump onto the higher platform. Make your way over the rooftops to the sword; it is in the top level of a building not far from Hotel Zanzibar. The building's roof has a large chunk missing, suggesting something hit it.
Note that if you have not already killed all of the enemies at the Hotel, obtaining this Sword will prompt an Ultra Elite to attack it.
- The Rex Easter egg does not always appear; sometimes, when it does appear, the Energy Sword has infinite charge.