I found in BF3 going prone was pretty handy in some tight corners and open fields. Traditionally Halo never had this, but Destiny isn't Halo, and going prone might be a needed ability when using some of the larger suppressive weapons or sniper rifles. Plus the benefit of conserving ammo if a player needs to wait out a Ai while being in a smaller detection box could be a life saving tool in the player kit while abroad in the open world.
Also I wouldn't mind some sort of climbing animation for players as well, so we can scale walls with say heavy foliage growing on it. This all plays to the Hunter class, but I could see it being universal only lets go with Titans climbing slower than both the Warlock and Hunter, while the Hunter is the faster of the three.
So if anybody remembers playing Turok I wouldn't mind some ability to leap across a chasm and grab onto a wall of vines and scale up the side of some Fallen Fortress to get the better of them.
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I would much prefer a tactical roll!