All 4 One is the collective name for the four signature guns of Jeanne, Bayonetta's enemy in the original Bayonetta game later ally in the second who appears in Ultimate as a Spirit. These guns have traces of features from the Luger P08 evident in them. Despite having an alternate costume based on Jeanne, Bayonetta does not use the All 4 One pistols for she still keeps her Love is Blues instead.
Beretta 92FS "Samurai Edge"
On November 29th, 2019 four Spirits from the Resident Evil franchise were added to the game with one of the Spirits being Jill Valentine as she was depicted in the 2002 remake of the original game, armed with the iconic S.T.A.R.S "Samurai Edge", a custom version of the Beretta 92FS.
Colt M1911A1
Naked Snake's Spirit depicts him with his iconic highly modified Colt M1911A1 with a silencer attached.
Desert Eagle Mark XIX
The Desert Eagle Mark XIX with a 10 inch barrel and a scope from Metal Gear Solid 4 is carried by Meryl Silverburgh's Spirit.
Heckler & Koch Mark 23
Much like during his previous appearance in Brawl, Snake keeps a Heckler & Koch Mark 23 in his holster but it cannot be used.
"Love is Blue"
Love is Blue is the collective name of Bayonetta's main pistols from Bayonetta 2 (which takes inspiration from the Mauser C96) and is appropriately featured in her alternate costumes based on her appearance from that game and is used in a number of her attacks.
Norinco Type 54
Joker from Persona 5 was added to the game as DLC on April 17, 2019 as part of the "Challenger Pack 1" and for his neutral special, he wields a gun.
Or more specifically, a Norinco Type 54 with a silver finish (known in Persona 5 as the Makaranov; in that game an airsoft replica operating like a real weapon due to the rules of the Metaverse) that can be fired in alternate directions, never runs out of ammunition or needs to be reloaded. When Joker's Persona Arsene comes out to fight alongside him after filling the Rebellion Gauge, the Type 54 becomes capable of rapid semi-automatic fire, a reference to the "Down Shot" maneuver from his home game.
"Scarborough Fair"
Highly based off of the Remington 1866 Derringer, Scarborough Fair is the collective name of Bayonetta's signature pistols from the first game in her eponymous series and are used in her alternate costumes that come from her appearance in it. In Super Smash Brothers, the difference between these and the Love is Blue are merely cosmetic as both weapons use the same attack animations and do the same amount of damage.
Shansi Type 17
EVA from Metal Gear Solid 3 appears in the game as a Spirit with her Shansi Type 17 drawn.
"Silver Ghost"
One of the other Resident Evil Spirits added into the game is Leon Kennedy; the Spirit is based on Leon as he appears in Resident Evil 4, complete with his fictional "Silver Ghost" handgun (a design drawing influence from the Heckler & Koch USP Tactical, the Smith & Wesson Sigma, and the Ruger P85).
"UAC EMG Sidearm"
The "UAC EMG Sidearm", a pistol from Doom (2016) that fires directed-energy beams instead of bullets, is available as the weapon of choice for the Doom Slayer Mii Fighter, which was released October 18th, 2021 as part of the final batch of DLC for the game. The EMG Sidearm used the Beretta 92FS as a base, a fitting choice due to the 92FS's presence in the Original Doom.
Enhancing Major Ocelot's Spirit after leveling it up to Level 99 will turn the Spirit into the Phantom Pain incarnation of Revolver Ocelot with his "Tornado-6" drawn. In Phantom Pain, the Tornado-6 is actually an altered Uragan-5 which in turn takes influence from Mateba series revolvers, while having the hexagonal cylinder design of the Chiappa Rhino series, and a break-action design similar to the MP-412 REX. Curiously, the Tornado-6 here seems to have a nickel finish in contrast to its appearance in Phantom Pain. The vector used by the Spirit is also used in an icon you can place on your Smash Tag as well.
Shotguns
Blunderbuss
Newcomer King K. Rool's neutral special has him using a Blunderbuss with a comically oversized muzzle, the weapon being a callback to the Kaptain K. Rool boss fight in Donkey Kong Country 2: Diddy's Kong Quest. The Blunderbuss can not only fire cannonballs but can vacuum up either the cannonball or other opponents and shoot them back out in different directions.
Sawed Off Shotgun
A Spirit featuring The Turks & Rufus Shinra from Final Fantasy VII is added into the game upon downloading Challenger Pack 8 featuring Sephiroth shows Rufus Shinra with his regular Sawn-off Double Barreled Shotgun.
Submachine Guns
"Hero Shot"
A Mii Gunner outfit of the character Marie from Splatoon 2 was made available on June 29th, 2020 to coincide with the release of DLC fighter Min Min from the ARMS series. Unlike many of the other outfits for the Mii Gunner where they use a blaster attached to their right arm, the weapon used for the Marie costume is a handheld weapon called the Hero Shot, a weapon from Splatoon 2 that is a dead ringer for the FN P90. Unlike the Splattershot used by the Inkling fighter, the Hero Shot cannot fire paint or cover other fighters in it, instead firing laser beams like all other blasters in the game.
Rifles
ACR
Among the other Resident Evil Spirits is Chris Redfield as he appeared in Resident Evil 6, armed with an ACR with a FAMAS style carrying handle. In Resident Evil 6, the ACR was called the "Assault Rifle For Special Tactics".
AR-15 Variant
Snake's Fighter Spirit, which is unlocked after you complete his Classic campaign for the first time, depicts him holding an AR-15 style rifle with an M16A2 style handguard and aftermarket sights. The angle the rifle is being held at makes it admittedly difficult for a more positive identification. Cartoonish M16s also appear in the Tank & Infantry Spirit from the Famicon Wars series.
"MRS-4"
The FAL-style "MRS-4" from Metal Gear Solid V is seen in the Spirit of Big Boss (or more specifically Venom Snake), which is unlocked after you enhance the Spirit of Naked Snake upon reaching Level 99 with it and is also seen on a Smash Tag icon that uses the same vector for Venom Snake. The rifle in turn is influenced by the Beretta SCP-70/90, the Imbel MD 97, the FN FNC, the SR 88, the Daewoo K2, and the Gwinn Firearms Bushmaster Rifle.
The aforementioned Gekko Spirit/stage scenery also have Browning M2HBs mounted on them.
C4
Both the regular and butterfly versions of the C4 return as Snake's down special, the only difference is this time it now has an obvious red light after being placed. Both versions of the C4 do the same amount of damage.
General Electric M134
The release of "Challenger Pack 8" which includes the famous Final Fantasy VII antagonist Sephiroth also coincides with the release of the Barret Wallace outfit for the Mii Gunner fighter, who uses a weapon that resembles a General Electric M134 just like Barret does. A Spirit of Barret is also added to the game upon downloading Challenger Pack 8.
M18 Smoke Grenade
Snake uses an M18 smoke grenade to signal the beginning of his new Final Smash called Covering Fire, which signals a rocket barrage after Snake marks his location.
M224 Mortar
The M224 Mortar from Metal Gear Solid 4 returns as Snake's up smash.
M60E3
A Spirit of Ralf Jones and Clark Still from the 1986 video game Ikari Warriors is added into the game upon the purchase of Challenger Pack 4. The Spirit depicts them both armed with short barreled M60E3s.
M67 Hand Grenade
The M67 hand grenades from Brawl return as Snake's neutral special, only this time they seem to be more oversized than in Brawl as the grenades are too big for Snake's hands, although this is likely so they can be more easily seen during gameplay. Snake can only throw two of these grenades at a time before having to wait for one of them to blow up.
Mk 2 Hand Grenade
The aforementioned Spirit of Ralf & Clark also shows Ralf pulling the pin off of a Mk 2 hand grenade with his teeth like the 80's action hero he is.
"Nikita Missile Launcher"
The "Nikita missile launcher" from Metal Gear Solid 2, which in turn resembles a FIM-92 Stinger, returns as Snake's side special.
RPG-7
The RPG-7 with a PGO-7 scope returns from Brawl as Snake's side smash.