The image of a Beretta 92FS is seen on a computer screen in the middle of "Folie a Deux". Reese Venek (Tommy Schrider) uses it in "The Ballad of Lady Frances". It's used by Bethesda (Chivonne Michelle) in "The Art of Sleights and Deceptions" and by a woman during a magic show demo. The 92FS is seen on Alpha Hawk's website in "Moving Target". The image of a 92FS is seen in "Hurt Me, Hurt You".
Beretta 92FS Inox
A Beretta 92FS Inox with wood grips is secured by Joan Watson (Lucy Liu) during an investigation in "The Art of Sleights and Deceptions".
Colt 1911
A Colt M1911 appears to be seen in "Hurt Me, Hurt You".
Glock 19
The Glock 19 is used by all NYPD officers as their main sidearm. Detective Marcus Bell (Jon Michael Hill) seems to use this instead of his Glock 17 as his main sidearm.
Glock 26
A Glock 26 is used by rogue Defense Intelligence Agency agent Anson Gephardt (Scott Shepard) in "Fidelity".
Nambu Type 14
A Nambu Type 14 is used as a murder weapon throughout "It Serves You Right to Suffer".
Smith & Wesson M&P
A Smith & Wesson M&P pistol with a stainless slide is seen with a SBK gangster near the end of "It Serves You Right to Suffer".
Revolvers
Smith & Wesson Model 19 Snub Nose
What appears to be a Smith & Wesson Model 19 Snub Nose is used by a murder suspect at the start of "Render, and Then Seize Her" (S05E03).
Smith & Wesson Model 60
What appears to be a Smith & Wesson Model 60 is used by Shinwell Johnson (Nelson Ellis) at the end of "Folie a Deux". Another Model 60 is seen in "To Catch a Predator Predator".
Smith & Wesson Model 681
A Smith & Wesson Model 681 is used in the revolver wheel, changing from the Taurus Model 689 in the opening sequence. It makes a return since the opening sequence is used again in the fifth season.
Taurus Model 689
Taurus Model 689 revolvers are used in the opening sequence of Elementary in a revolver wheel. Like the Model 681, it makes a return since the opening sequence is used again in the fifth season.
Submachine Guns
Ingram MAC-10
An Ingram MAC-10 is used during an attempted hit in "Fidelity".
Assault Rifles
AKS-74U
What appears to be an AKS-74U is seen in a media photo of a Mujahid fighter in "Crowned Clown, Downtown Brown"
Colt LE Carbine
The Colt Law Enforcement Carbine is used in the season less frequently with the NYPD ESU. Somehow, they're seen with New York National Guard soldiers in "Wrong Side of the Road".
Colt M4A1
The Colt M4A1 is seen with American law enforcement personnel. Some are seen in an archived photo in "Bang Bang Shoot Cutie".
Colt Model 933
The Colt Model 933 is used by a few NYPD ESU operators in the season. A FBI SWAT assaulter appears to be using one in a standoff at the end of "Fidelity".
Shotguns
Remington 870 MCS Masterkey
A short Remington 870 MCS Masterkey with a Picatinny rail and pistol grip is used by Jack Brunelle (Isiah Whitlock Jr.) when he announces a hostage crisis in "Over a Barrel".
Sniper Rifles
Remington M24
A Remington M24 is seen in "Bang Bang Shoot Cutie" with Marjan Durrani (Mohit Gautam) as he prepares to shoot his own sister.
Unknown
Other
Advanced Taser X26
A X26 Taser is used by Watson to take out a distressed person at the start of "Folie a Deux".