Type-33 needler

Stats Rate of fire: Average to high (3-10 per second, increases  with continued fire) Damage per hit: Low to very high (Explosion will occur per 7  needles in target) Range: Short to medium (most effective at short range) Accuracy: High (Needles are homing) Magazine size: 20 needles (30 in Halo 2) Maximum ammo: 90 needles (including fully loaded magazine)

Advantages
This weapon fires tracking needles that embed themselves in the flesh of a target. Rate of fire increases with continuous fire, up to 20 rounds in 2 seconds (one complete clip). If 7 or more needles accumulate in the target, an explosion will occur, killing the target and causing splash damage. Needles can penetrate the energy shields of Elites/Sentinels/Spartans (and the Master Chief), but they bounce off the hand-held shields of Jackals and Hunters.

Insightful players will find the needler can often be the key to victory in certain situations. For instance, on the level "Keyes" in Halo:PC, players will encounter three or four Flood combat forms situated on ledges above the player. Rushing through means dying in a gauntlet of fire from an elevated position. Grabbing a needler and firing at each Flood from behind a conveniently located stationary shield will allow the player to safely destroy each enemy. Furthermore, each Flood is positioned in shadow making it extremely difficult to effectively engage them with other direct-fire weapons; the needler solves this problem by homing in on these otherwise nearly invisible enemies. They can also be effective against Elites by either killing them outright or forcing them to dodge or retreat, giving players a chance to reposition themselves for an advantage.

In Halo 2, paired needlers mean certain death for Brutes, Jackal snipers, and the jetpack-borne Ranger Elites; deadly volleys of needles home in on and destroy targets, allowing players to retreat back to cover, sometimes before enemies even know they're under attack. This tactic can also work when faced with overwhelming firepower from enemy squads tactically positioned at an advantage. For instance, during the level "Regret", players will exit the temples before boarding the final gondola. The door is heavily covered by Elites and Drones. Well-timed needler bursts and retreats back to cover will clear away the Drones and possibly at least one Elite. Further up the trail, sharp-eyed players can find a spot from which to "snipe" the squad of Elites, Jackals, and Grunts among the ruins below. If you still have any squadmates left alive, you can provide effective cover fire for them, especially if you've armed them with powerful weapons (another overlooked and undervalued tactic).

This also works in Halo:PC, especially on the level "Halo". During "Flawless Cowboy" as you're rescuing your crewmates, you may find yourself severely outnumbered and under heavy Covenant fire. Taking cover and occasionally popping out with a needler burst is a great way to prolong your survival and chip away at the enemy's numeric advantage.

Disadvantages
The needles are slow, and are not effective against vehicles. The needles also take time to hit/explode on the target, leaving the target time to move in and cause some of the explosion to damage the shooter. It is nearly impossible to hit invisible Elites with the Needler, as they do not home to camouflaged targets. While shooting Flood with it may be effective, they can often come close enough to damage the player with the splash damage from the explosion, due to Flood forms' speed.

Influence
The needler was inspired by the Flechette gun from the Marathon series.

Multiplayer Role
The needler is one of the worst weapons in multiplayer. The homing qualities of the needle have almost no effect on targets at medium range and the only way a player could get kills with it was if an opponent was running in a straight direction towards or away from the needler-wielder, or if the target was standing still. While it does prove useful in close up fights. It is useless against competent players, and is not often found commonly in most multiplayer maps.

Effective Against
Elites, Grunts, Brutes, Sentinels, small groups of tightly packed Flood.