Found this stuff in the bungie forums
As of right now, the X-button is Deploy Equipment. The will be a number of items that can be picked up and deployed in certain situations. You would be able to hold only one type of these weapons and can only be used through the X button.
-Bubble Shield
-Gravity Lift
-Trip Mine
-Deployable Torrent
Bubble Shield is deployed onto the ground, then rolls to the gravity or stays put. The player won’t be able to fire while inside it or players won’t be able to fire at the person inside the shield while it is activated.
Gravity Lift can be strategically placed to allow a person to boosted to new heights undetected by the enemy. This means no more people camping the gravity lifts because it can be deployed anywhere anytime.
Trip Mine can only be deployed once before you have to pick it up again, meaning it would be strategically placed anywhere on the map to destroy an enemy vehicle. This could prove to be a very good for making drivers very causes around other team.
Deployable Turret will be carried to any spot, and then placed there to allow better position. It would be very hard to be picked off the turret because you can move, but it takes time to set it up.
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So, I'm gonna set the turret right next to the overshield and just camp all day picking off fools. (yes, I'm an asshat)