Deputy Chief Brenda Leigh Johnson (Kyra Sedgwick) carries the Glock 26 as her sidearm. Detective Irene Daniels (Gina Ravera) carried the Glock 26 as well from seasons 1 through 4.
Glock 19
Lt. Mike Tao (Michael Paul Chan) carries the Glock 19 as his duty weapon. The Glock 19 is also carried by FBI Special Agent Fritz Howard (Jon Tenney).
Beretta 92FS
Lt. Louie Provenza (G.W. Bailey), Detective Sanchez (Raymond Cruz) and Sgt. David Gabriel (Corey Reynolds) carry the LAPD's previously standard issue Beretta 92FS as their onduty sidearms. The detectives are notably seen drawing their sidearms in Season 4's "Time Bomb".
In "Time Bomb" (S4E10), a full-size Uzi is found in a garage along with an M4A1.
Rifles
M4A1
In "Time Bomb" (S4E10), the Major Crimes Division engages in a shootout at a shopping mall against a heavily armed and armored teenage spree killer who is carrying an M4A1 carbine assault rifle. This gun is used to wound Detective Sanchez.