Ranged weapon-switching

From Halopedia, the Halo wiki

This skill is used to grab weapons from afar at the cost of at least one grenade (or explosive device). This is a trick that is easy to learn but hard to master.

First, throw the grenade just behind a weapon of choice such that the weapon is between you and the grenade. When the it explodes, the weapon will go flying over towards you (if you aimed right). Jump just as the weapon gets past you and hold (X). If done correctly, you should have the weapon in your grasp. If you already have that weapon in your disposal, you will just get the ammo.

You may perform this with:

This is very useful if you are in dire need of another weapon to suit the situation, or if you need ammo.