Rifle

In the actual sense of the word, a "rifle" is a weapon with a spiral grooved barrel that imparts a spin on a projectile to obtain better levels of accuracy than a smoothbore weapon, such as a musket or a shotgun. However, "rifle" is sometimes also used as a technically erroneous term for certain directed energy weapons.

Overview
When regarding human weapons, there are a few forms of the word "rifle" used. An "assault rifle" is a select-fire weapon that fires an intermediate rifle round. A "battle rifle" fires a large full-size rifle round and is usually, but not always, semi-automatic and often has a long full-size barrel. A "sniper rifle" can fire various high-caliber ammunition variants, and are almost exclusively semi-automatic. Their goal is to achieve high levels of accuracy and lethality, and have longer ranges than assault or battle rifles.

Regarding Covenant and Forerunner weapons, the term "rifle" is used not to describe the technical nature of the weapon itself, but in the role it plays on the battlefield. For example, the plasma pistol and plasma rifle, while similar, are used for two different purposes. A rifle is larger than a pistol, often requiring both hands to use, but is smaller than a heavy weapon, such as the Brute shot or fuel rod cannon. This applies to both the plasma rifle and the beam rifle. The Covenant carbine is also considered a rifle and the spiker can fit into this list as well.

Assault rifles
Assault rifles are military service weapons that fire intermediate rifle cartridges; merging the light machine gun's firepower with the submachine gun's compact design.

MA Series

 * MA1 Individual Combat Weapon System - The original MA rifle, precursor to all current MA variants.
 * MA2B Individual Combat Weapon System - Successor to the MA1. Functionally similar to the the MA5B. Occasionally used by Special Forces operators.
 * MA3A Individual Combat Weapon System - The precursor to the MA5B assault rifle. Retired from service, remains popular on the black market and among insurrectionist groups.

MA5 series

 * MA37 Individual Combat Weapon System - In service with the UNSC Army up until the Fall of Reach. Featured in Halo: Reach.
 * MA5B Individual Combat Weapon System - A MA5 variant with a 60-round magazine configuration. Featured in Halo: Combat Evolved.
 * MA5C Individual Combat Weapon System - An improvement of the MA5BA with a 32-round magazine configuration.Featured in Halo 3.
 * MA5D Individual Combat Weapon System - A MA5 variant with a 32-round magazine configuration.Featured in Halo 4.
 * MA5K Carbine - Carbine variant, wielded by Special Forces units such as the SPARTAN-IIIs.

Battle rifles
Battle rifles are military service weapons that fires a full-power rifle cartridge; providing greater effective range, penetration, and stopping power than assault rifles.

BR55 series

 * XBR55 Battle Rifle - Halo: Contact Harvest-prototype battle rifle.
 * BR55 Battle Rifle - Shoulder-fired firearm firing in 3-round bursts. Featured in Halo 2.
 * BR55 Heavy Barrel Service Rifle - A heavy-barreled variant of the BR55. Featured in Halo 3.

Other battle rifles

 * BR85 Heavy Barrel Service Rifle - Post-war successor to the BR55 series. Featured in Halo 4.

Carbines
Carbines are shortened light-weight versions of full rifles, firing the same ammunition at a lower velocity due to a shorter barrel length.
 * Asymmetric Recoilless Carbine-920 - Compact-channel linear accelerator carbine, fires high-explosive rounds at extreme velocities.
 * MA2B Individual Combat Weapon System - Successor to the MA1. Functionally similar to the the MA5B. Occasionally used by Special Forces operators.
 * MA5K Carbine - Uncommon carbine variant, wielded by Special Forces units such as the SPARTAN-IIIs.

Marksman rifles
Marksman rifles are military service weapons, built for greater precision than an assault rifle or battle rifle, using either the standard service rifle cartridge, or a more accurate variant of the cartridge; used to fill the "marksmanship gap" between the battle rifle and the sniper rifle.
 * M392 Designated Marksman Rifle - Accurate select-fire (semi-automatic in-game), medium-range rifle. Better known as the DMR. Featured in Halo: Reach.
 * M395 Designated Marksman Rifle - Post-war successor to the M392 DMR. Featured in Halo 4.

Nonlinear rifles

 * M6 Grindell/Galilean Nonlinear Rifle - Shoulder-fired, anti-vehicular, directed energy weapon. Featured in Halo 3, Halo Wars, Halo 3: ODST and Halo Reach. Better known as the Spartan laser.

Recoilless rifles

 * Asymmetric Recoilless Carbine-920 - Compact-channel linear accelerator carbine, fires high-explosive rounds at extreme velocities. Better known as the railgun. Featured in Halo 4.
 * M149 Recoilless Rifle - United Nations Space Command weapon used during the Human-Covenant War. Better known as the Magellan.
 * M99 Special Application Scoped Rifle - Man-portable miniaturized Magnetic Accelerator Cannon. Used by Avery Johnson in Operation: KALEIDOSCOPE.

Sniper rifles
Sniper rifles are military service weapons that fires anti-matériel/anti-vehicular rifle cartridge; used when precision target-acquisition, extended-range, and lethal force is needed.

SRS99 series

 * Sniper Rifle System 99 Anti-Matériel - Long-range, shoulder-fired sniper rifle, fire various 14.5x114mm ammunition variants. Featured in Halo: Reach.
 * Sniper Rifle System 99C-Series 2 Anti-Matériel - Variant of the original SRS-99. Featured in Halo 2.
 * Sniper Rifle System 99C-Series 2 Anti-Matériel B - Variant of the SRS99C-S2 AM. Featured in Halo: Ghosts of Onyx.
 * Sniper Rifle System 99D-Series 2 Anti-Matériel - Variant of the SRS99C-S2 AM. Featured in Halo 3.
 * Sniper Rifle System 99-Series 5 Anti-Matériel - Post-war successor to S2 variants. Featured in Halo 4.

Other sniper rifles

 * M99 Special Application Scoped Rifle - Man-portable miniaturized Magnetic Accelerator Cannon. Better known as the Stanchion. Used by Avery Johnson in Operation: KALEIDOSCOPE.

Ballistic/Projectile Rifles

 * Type-33 Guided Munitions Launcher - Handheld sidearm, fires homing crystalline ammunition. Better known as the needler.
 * Type-31 Rifle - Medium-range cousin of the needler. Analogous to the DMR. Better known as the needle rifle. Featured in Halo: Reach.
 * Type-25 Carbine - Handheld spike rifle. Analogous to the SMG. Better known as the Brute spiker.
 * Type-51 Carbine - Scaled-down, anti-infantry version of the fuel rod cannon. Analogous to the battle rifle. Better known as the Covenant carbine.

Particle Beam Rifles

 * Type-50 Sniper Rifle System - Long-range shoulder-fired weapon, primarily used by Kig-yar Snipers. Analogous to the SRS99 sniper rifles. Better known as the beam rifle. Featured in Halo 2, Halo 3, Halo Wars, and Halo 3: ODST.

Plasma Rifles

 * Type-25 Directed Energy Rifle - Handheld plasma-operated weapon typically wielded by Sangheili. Better known as the plasma rifle.
 * Type-25 Directed Energy Rifle/Jiralhanae variant - Variant of the standard plasma rifle wielded exclusively by Jiralhanae, with superior rate of fire. Featured in Halo 2 and Halo 3: ODST.
 * Type-50 Directed Energy Rifle/Heavy - Shoulder-fired plasma-operated weapon-variant that fires explosive bolts of superheated plasma. Better known as the concussion rifle.
 * Type-51 Directed Energy Rifle/Improved - Shoulder-fired plasma-operated weapon used mostly by Sangheili. Analogous to the MA5 series assault rifles. Better known as the plasma repeater. Featured in Halo: Reach.
 * Type-55 Directed Energy Rifle/Advanced - Handheld plasma-operated successor to the widely used Type-25 DER typically wielded by Sangheili. Better known as the storm rifle. Featured in Halo 4.
 * Type-52 Special Applications Rifle - Sniper weapon, fires continuous beam of magnetically contained plasma. Better known as the focus rifle. Featured in Halo: Reach.

Hard Light Rifles

 * Z-130 Suppressor - The energy channel weapon fires bolts of charged Hardlight that pierce and destroy organic material of any type. The automatic fire of the Z-130 made the weapon a favorite for Forerunner troops fighting against the Flood. Utilized by Promethean Knights during the Battle of Requiem. Featured in Halo 4.
 * Z-180 Close Combat Rifle/Asymmetric Engagement Mitigator - Short-range, wide-spread energy channel weapon with ricocheting Hardlight shot has terrifying killing potential. The X-180 gained popularity in the latter part of the Forerunner-Flood war. Better known as the Scattershot. Featured in Halo 4.
 * Z-250 Lightrifle - Mid- to long-range energy channel weapon. A Forerunner weapon used by Promethean Knights on Reqiuem. The Z-250 is comparable to both human M395 DMR and BR85HB-SR, allowing for burst fire when shot from the hip and precision targeting when scope. Primary-mode fires a three round burst, analogous to the BR85HB-SR. Secondary-mode fires single shot that is more powerful while scoped, analogous to the M395 DMR and the Type-51 Carbine. Featured in Halo 4.
 * Z-750 Special Application Sniper Rifle - energy channel weapon includes two core-mounted particle accelerators with unparalleled stopping power to bring down distant foes with one shot. Used by Forerunner Promethean Knight units encountered on Requiem. Better known as the Binary rifle. Featured in Halo 4.

Other light rifles

 * Z-390 Anti-Material High-Explosive Munitions Rifle - energy channel weapon that fires several streams of explosive particles along multiple paths that detonate and spread upon impact with a target. Mixing traits of a rocket launcher, shotgun, and flamethrower, it's a highly destructive weapon. Better known as the Incineration cannon. Featured in Halo 4.
 * Z-110 Directed Energy Pistol - Energy channel weapon particle dilator with burst function at close range, designed as a close- to mid-range precision weapon that devastates organic matter. Historically, the Z-110 came into use at the end of the first century of conflict between the Forerunners and the Flood, and remained in use until the war ended two centuries later. Better known as the Boltshot. Featured in Halo 4.

Deleted material

 * Gravity rifle - A Covenant long-range rifle cut from Halo: Combat Evolved.