Sangheili Point Defense Gauntlet
From Halopedia, the Halo wiki
Early in the development of Halo, Elites carried an arm shield, similar to the Jackal Point Defense Gauntlets carried by Jackals. This shield was later replaced by the Elite Personal Energy Shield. While the Elite Arm Shield was never seen in game, it was used by Rtas 'Vadum in the Halo Graphic Novel.
There is a rumor that it was swapped for the full body shields the Elites have now. The player may have needed to wear down each of the 3 layers of the shield to get a clear shot and after some time it would regenerate, however this is still just a rumor.