Miguel Ortega has released a cool mod for Halo 4 that lets you experience it in third-person mode. In order to showcase his mod, Ortega has also released a gameplay video that you can find below.
Going into slightly more details, this mod allows you to experience the entire campaign of Halo 4 in a third-person view. The modder has also introduced some gameplay changes.
For instance, Ortega has removed all HUD elements (such as screen shake) and has altered most of the oversized reticles. Additionally, he removed the energy bar and has given more ammo and accuracy to the human weapons. Active Shield is also infinite (and players can toggle it off and on whenever they want).
Lastly, the modder removed the radar, as well as the zone boundaries in some levels.