Not eligible as a main article since it's a mobile game, so I'll work on it here :) Sadly, my graphics settings are restricted to low quality.
The following weapons appear in the video game Call of Duty: Mobile:
The "J358" is a revolver loosely based on the Smith & Wesson Model 327 Performance Center M&P R8. It has wooden grips, and uses .45 caliber ammunition in Battle Royale mode. It holds 6 rounds by default, but somehow has an "extended mag" attachment option that increases the capacity to 8 rounds (which actually matches the cylinder capacity of the real S&W Model 327).
Springfield Armory 1911
SRM Arms Model 1216
The SRM Arms Model 1216 appears as the "HS2126". Unlike its counterpart from Black Ops II, one pull of the trigger automatically fires four rounds before rotating the magazine, essentially making it a burst-firing shotgun.
Winchester Model 1887
A heavily modified sawed-off Winchester Model 1887 appears as the "HS0405".
The "HG 40", a futuristic MP40 from Black Ops III, appears in the game with even more alterations to the model.
The Modern Sub Machine Carbine appears in the game.
The FN P90-based "PDW-57" from Black Ops II returns in the game.
The Ruger MP9-based "Pharo" from Black Ops III was added in the Season 2.
Rifles & Carbines
The AK-102 returns from Call of Duty Online as the "AK117".
The AKM appears, still referred to as the earlier AK-47.
The "Pumpkin Head" variant is a Halloween-decorated rifle based on Black Ops 4’s "KN-57" (which itself was based on the 2015 prototype of the AK-12). Like that weapon, it is loaded with a 5.45x39mm magazine.
The AKS-74U appears, modeled after the modified version from Call of Duty Online, and still classed as a submachine gun. The in-game name was changed from "AKS-74U" to "RUS-79U" during the Season 3.
The modified AKU-94 from Call of Duty Online returns as the "BK57".
A custom AR-15-patterned rifle appears as the "M4". It has a handguard which appears to be a hybrid between HWK KeyMod Free Float Handguard, Titan Handguard and Fortis Night Rail and a stock that appears to be a hybrid between a Magpul MOE SL and a Steyr AUG's stock.
The "HBRa3" from Advanced Warfare, a futuristic weapon based on the Robinson Armament XCR, was added to the game in the Season 3.
Heckler & Koch G36K
A heavily modified Heckler & Koch G36K appears in the game. It is referred to as the "LK24", and the model takes some design cues from the "G37H" seen in Call of Duty Online. It lacks a carrying handle, and has a custom handguard and telescoping stock, and an AR fire control group. While H&K does offer such fire control lowers for G36 rifles, the in-game version is different, as it has "Safe"/"Semi" markings as opposed to the peculiar H&K bullet pictograms.
The "Royal Crimson" variant gains a rail top carry handle, along with various differences including the fire selector, handguard and stock.
The "ICR-1" from Black Ops III, a futuristic assault rifle based on the Heckler & Koch HK416, was added in the Season 2.
The AK-200-esque "KN-44" from Black Ops III was added during Season 3. Prior to this, the AK-47 had a variant called "Red Action", which is based on that same "KN-44".
The M16A4 appears simply as the "M16". It uses the Modern Warfare Remastered model with some minor alterations.
Accuracy International AS50
The Accuracy International AS50 appears as the "Arctic .50", similarly to Call of Duty Online.
The "DL Q33" is a bolt-action sniper rifle that appears to be loosely inspired by the Victrix Corvus.
The "XPR-50", a semi-automatic sniper rifle somewhat resembling the bolt-action Barrett Model 98 Bravo, returns from Black Ops II and Black Ops III.
DS Arms RPD
The DS Arms RPD from Call of Duty Online returns.
Handheld General Dynamics GAU-19/A
The futuristic handheld General Dynamics GAU-19/A from Black Ops II returns as the "Death Machine". It is available as an "operator skill", and is also equipped on the "XS1 Goliath" armor killstreak.
A modified L86A1 appears as the "UL736".
The "M4LMG", a squad automatic weapon seemingly based on a Barrett REC7, returns from Call of Duty Online.
Norinco QBB Hybrid
A hybrid between the QBB-95-1 and the QBB-97 appears as the "S36". It has a selector switch above the pistol grip like the QBB-95-1, but feeds from an AR-15 style magazine like the QBB-97, as well as having a QBZ-95 style trigger guard.
The Pansarskott m/86 from Call of Duty Online returns as the "SMRS".
The "War Machine" is a futuristic grenade launcher based on the Milkor MGL Mk 1L. It is available as an "operator skill".
M26 hand grenade
Three unusable M26 hand grenades can be seen on Firebreak's character model.
General Dynamics GAU-19/A
A tripod-mounted version of the aforementioned GAU-19/A is used for the unmanned sentry gun killstreak. The gun is also mounted on the "Antelope A20" assault vehicle in Battle Royale mode.
Unusable low poly machine guns seemingly supposed to represent the M240D can be seen mounted on some tanks.
Colt AR-15A3 Tactical Carbine
A drawing of a Colt AR-15A3 Tactical Carbine is seen on weapon XP cards.
Too much fictional
The "KRM-262" pump-action shotgun from Black Ops III was added in the Season 3.
The "Razorback" from Black Ops III, a submachine gun bearing a resemblance to the fictional "Thor PDW", was added in the Season 2.
The "Man-O-War" rifle from Black Ops III was added in the Season 2.