Kig-Yar point defense gauntlet

Jackal Point Defense Gauntlets are arm held energy shields mainly used by the Covenant Jackals for protection from enemy fire. Worn on the forearm, they create a barrier that can deflect most solid projectile weaponery.

Damage Resistance
The shield of the point defense gauntlet reflects its' current charge by changing color gradually from its original color to red before it deactivates completely.

In Halo 2, the shield appears to have been weakened. It is now possible (albeit difficult), to bring down a shield with projectile weaponry, and a sniper round to the central dot will collapse it and stun the Jackal.

Halo 3 era jackal shields are the strongest yet, being uncollapsible by standard projecticle UNSC weapons (even to shots to the central dot), and melees no longer instantly kill the Jackal, they just deactivate the shield. Jackals also will not flinch when ammunition hits the edges of their shields, they will only flinch when a bullet connects with their body (particularly the hand exposed by the firing notch). It is more susceptible to the Plasma Rifle and Sentinel Beam now however.

UNSC Weapons
The Jackal Point Defense Gauntlet is completely resistant to the UNSC's metallic projectile ammunition. Most UNSC weaponry will simply bounce off the shields. Even the SRS99D-S2 AM Sniper Rifle's large 14.5mm APFSDS rounds are deflected (except when fired at the central shield emitter in Halo 2).

However continuous fire from certain weapons will cause the Jackal to momentarily drop its shield. The Warthog's M41 LAAG, AIE-486H Heavy Machine Gun (and curiously MA5B and SMG in Halos 1 and 2) rounds will cause the Jackal to flinch allowing the rest of the weapon's bullets to eliminate the Jackal. This may be due to the physical weakness of the Jackal as the bullets themselves are deflected.

The few human weapons that can penetrate the shield are explosive weapons such as the Rocket Launcher, missile pod, and the Spartan Laser.

Covenant Weapons
Alternatively, the point defense gauntlet has very low resistance towards Covenant Plasma-based weaponry. Plasma fire will deplete the shield's strength until they completely collapse. A few shots from a Plasma Rifle or a Plasma Pistol overcharged shot will successfully collapse the shield and may also cause the Jackal to flee.

Strangely the Covenant Carbine, a projectile weapon, can also deplete the shield in Halo 2.

Grenades
Explosions from grenades can collapse the shield and kill the Jackal. It should be noted that the Plasma Grenade and the Spike Grenade will not stick to shield (though in preproduction it was planned for the Spike Grenade to have this ability) but can still destroy the shield and the Jackal if it's near the explosion.

Melee
In Halo: Combat Evolved a direct hit to the shield will knock it backwards into the Jackal, sending a power surge through the Jackal's body and killing it. However, on Heroic and Legendary, it will often take more than one attack. Similar to most enemies, Jackals flinch when hit with a melee attack. In Halo 2 the shield now provides the Jackals with limited melee protection but in Halo 3 a melee attack will just collapse the shield.

Trivia

 * In the first Teaser of Halo: Combat Evolved a group of UNSC Marines inside a Forerunner complex engage with a Major Domo Elite with a triple-layered personal arm shield similar to the Jackal's.
 * In Halo 2, the Arbiter's zoom outline resembles that of a horizontal Jackal Energy Shield from Halo: Combat Evolved.
 * Sniper Jackals wear point defense gauntlets but never use them, even after dropping their rifles or carbines and fleeing.
 * It seems that Rtas 'Vadum has his own personal arm shield. This can be seen in the Halo Graphic Novel.
 * Point Defense Gauntlets were often used by early Spartans who lacked shielding or by Spartans and Elites who wanted enhanced shielding.
 * The MJOLNIR armor system was reverse engineered from a Point Defense Gauntlet.
 * The shield seems to be a dual wieldable item, as Jackals are never seen holding a weapon in their shield hand, as this would interfere with their aim and posture, and the shield may get in the way of their weapon (one exception is in a Halo 2 glitch where the Arbiter could give shield bearing Jackals two-handed weapons).
 * Jackals are the only Halo characters that are left-handed.
 * Apparently, Jackal shields in the novels run out of energy.
 * Spartan 3's were specily trained in using them because their SPI armor did not have a shieled.

Related Links

 * Energy Shields
 * Overshield
 * Elite Personal Energy Shield
 * Jackals
 * Shielded Flood Carriers