The Beretta Cheetah, also known by its original model name of "Series 81", is a line of compact blowback operated semi-automatic pistols designed and manufactured by Beretta of Italy. They were introduced in 1976 and include models in .32 ACP (Models 81 and 82), .380 ACP (9 mm Short) (Models 83, 84, 85 and 86) and .22 LR (Models 87, 87 Target and 89). The 84F is a modification to "Series 81", these models are chambered for the .380 ACP (9 mm Short) cartridge. The 84 has a double stacked magazine with 13 round capacity and has a 3.81" barrel.
Jesse Pinkman buys and plans to use a Beretta 84F to take revenge on drug dealers who killed Tomás Cantillo, but he never fires it as Walt intervenes with his car. He later uses it to kill Gale Boetticher.
In Madrigal, Mike Ehrmantraut uses a supressed Berettah Cheetah to kill his former man Chris Mara, at the conclusion of the episode he is seen checking it and later threatening the paranoid Madrigal executive Lydia Rodarte-Quayle with it.