M45 shotgun/Gameplay

Halo: Reach

 * The M45 Shotgun is more powerful than the M90A from Halo 3 and Halo 3: ODST. The pellets have a tighter grouping and the range is superior as well, which also makes it harder to hit multiple enemies at close range.
 * Although this change is hardly noticeable, impact force can be noticed as the damage has been increased.
 * The Shotgun functions very well in small confined maps, hence why it should be used as a "corridor sweeper" due to its extreme close range damage.
 * However, its increased damage means it has more recoil than the M90A.
 * It should be paired with a medium/long-range weapon like an Assault Rifle or DMR in case the player doesn't land a killing blow with the Shotgun on the first shot.

Halo: Combat Evolved Anniversary

 * The M45E Shotgun is exactly identical in performance to the M90 from the original game.

Halo 4

 * The M45D Shotgun has much higher range, lower damage falloff, and more power than the previous Shotguns.
 * As a close-quarters power weapon, the Shotgun is a one-shot kill weapon and should be used for close encounters.
 * It notably destroys enemy shields, particularly Elites, and kills Promethean Knights in two shots.
 * The Shotgun differs from the Scattershot with a higher lethal range, hitscan properties, a larger magazine size of 6 shells, and more total ammunition carried but with a lower rate of fire and a lower effective range.
 * In the campaign, the Shotgun first appears in Requiem but can be missed until Infinity. It appears again in Composer.

Halo 5: Guardians

 * The M45D Shotgun operates similarly to the previous version, but with these changes:
 * Like with all other weapons in the game, smart scope can be used to tighten the weapon's pellet spread for increased accuracy with a trade-off of increased recoil.
 * Its base range has been increased from its previous renditions to 8.40 m (27.56 ft) when hipfired and 10.10 m (33.13 ft) with smart scope.
 * It now has 5 shells per magazine, the same as the Scattershot.
 * Also like the Scattershot, it has a light on the barrel that can't be turned off, giving opponents slight warning of your presence.
 * However, the player should still exercise caution when using the Shotgun, despite its improvements, as it still features the problem of pellet inconsistency.
 * In the campaign, the Shotgun is first obtained normally in Blue Team, but can be obtained earlier in Osiris either via a Legendary-exclusive secret or by doing the level on Co-op and playing as Edward Buck.
 * Buck spawns with a Shotgun as his primary weapon in Osiris, both as an AI-controlled NPC and as a human-controlled player character. In all later levels, though, he spawns with an Assault Rifle.
 * Warzone features three additional variants:
 * Lawgiver: an improved variant with a slightly higher rate of fire, more accuracy, higher damage, and no recoil. This weapon comes in handy for intense close range engagements, where its higher rate of fire and better accuracy allows more kills to be scored.
 * Blaze of Glory: an advanced variant with Kinetic Bolts that provide the weapon even greater accuracy, an even higher rate of fire, strong knockback and damage against vehicles, and the ability to have its entire magazine reload with one shell. This variant is effective for anti-vehicle engagements and longer range combat. When Smart Scoped, it can kill an enemy Spartan with a single shot from a far longer range than any other shotgun, and makes it absolutely lethal in anything with even slightly close quarters. Defenders of Warzone bases should highly value this extremely powerful weapon. In fact, it can even pulverize light vehicles in as little as half a magazine.
 * It can also be found in the campaign level Blue Team, where it can be useful when fighting Hunters.
 * Combined with a Damage Boost and/or a Speed Boost, the Blaze of Glory can outperform even the Didact's Signet.
 * Oathsworn: Kelly-087's Mythic variant with a Speed Boost built in. It is basically the Lawgiver with slightly more accuracy and the aforementioned Speed Boost built in, which allows for quick hit-and-run combat more easily.
 * The Blaze of Glory is a better choice, though, as it outperforms the Oathsworn in every category except the addition of the Speed Boost, which the player must manually activate.
 * Alternatively, put on an Active Camo and the Blaze of Glory to become a one-Spartan base-assault/defense machine. Crouch walk close to your foes and obliterate them with a single shot. Those playing Warzone Turbo, be wary of the Blaze Camo Rush.
 * In the campaign, the Oathsworn is also Kelly's preferred starting weapon, although the campaign version of the Oathsworn is functionally identical to a normal Shotgun.