The spiker

The Type-25 Carbine is an automatic fire, magazine fed, double barrel weapon, that fires metal spikes that appear to be superheated by some sort of electrical discharge that occurs before the spike is shot from the barrel of the weapon. Two large blades made of tungsten carbide,[2] an extremely strong and durable material, are mounted under the barrel of the weapon, increasing its close quarters effectiveness. The Spiker ammunition is fed into the weapon via a small drum magazine with a 40-round capacity. The drum magazine is located on the underside of the weapon, behind the blade and in front of the trigger.
This weapon resembles human technology more closely than it does the other weapons in the Covenant’s arsenal. It performs admirably in a variety of environments; it is a widely held belief that the weapon could sit unattended for several weeks in an active latrine and still operate as issued with no maintenance performed on it. Unfortunately this is not far from the truth. Though it was first observed over a quarter century ago[3] this weapon has not been seen in the hands of front line troops until just recently. The Spiker is based on the Jiralhanae's native pre-Covenant technology, meaning it has been in use since they first learned how to create a firearm. Although the Spiker is classified as a Carbine, it is more of a counterpart to the UNSC's M7 SMG, having very similar range and penetration capabilities.
[edit]Advantages
In the field, Brute Spikers have similar penetration and lethal range to the UNSC M7 SMG, but there are a few key differences. Unlike SMGs, there is little recoil, and therefore almost zero “rise” when using them in their default, full-automatic setting. This actually makes them a little more efficient and accurate than the SMG in combat situations, since there is no need to adjust aim to compensate for recoil. The spike's high velocity and kinetic impact against shields is high, although the rounds are simply deflected or melted by the energy shield before inflicting damage to the underlying structure. The Spiker can usually kill a heavily armored and shielded target with a single magazine. The spikes do terrible damage to human flesh, and can tear through armor with ease, creating devastating wounds that are extremely painful for those who survive an attack.[4] Its two large blades are very deadly against shielded and unshielded infantry at close range, as they can be used to either slash or stab an enemy with fatal effects. A SPARTAN-II or an Elite can duel-wield Spikers doubling their firepower.I have got this info from halopedia.com