The knife is a moderate weapon that allows the player to attack without a firearm and, in Grand Theft Auto: San Andreas, allows stealth kills that don't attract unwanted attention. It takes up the "melee" weapon slot.
In GTA San Andreas some prostitutes wield the knife. It is used in many missions in the game like Madd Dogg's Rhymes, Amphibious Assault, The Da Nang Thang, Dam and Blast and Vertical Bird. The Knife is more than just a simple melee weapon. If CJ is aiming behind an opponent, he will execute a stealth kill, quietly slitting the victim's throat, useful when the player is trying to avoid detection and doesn't have a Silenced 9mm. The Knife only produces one wanted star when used to stealth kill a police officer.
The GTA IV rendition of the Knife resembles the knife portrayed by Sylvester Stallone in the Rambo movies, and is similar in size and shape to the Buck-184 Buckmaster survival knife. It can be purchased from Little Jacob for the staggering amount of $100. Alternatively, it can be picked up from Eddie Low during his second encounter. It can also be taken from the second enemy in the mission Bleed Out. Although silent kills like in GTA San Andreas are not in the game, 5 to 6 strikes with the knife will kill an opponent, and it will not warrant the player a wanted level. This can easily kill an enemy on single player or multiplayer because 4 to 6 quick taps of the[1] button on the Playstation or the Y button on Xbox 360 while locked on with this will either kill or almost kill anyone. Armor does not protect against knife attacks.
Locations
Grand Theft Auto: Vice City
Ocean Beach, Vice Beach - Can be found at the southernmost end of the series of back alleys.
South Slopes, Broker - Can be found in an alley to the south of Hickock St.
Rotterdam Hill, Broker - A Knife is at the far end of an alley south of Brucie's apartment off Asparagus Ave, and another Knife is in the alley behind Jermaine Andrews' apartment building on Mohawk Ave.
Schottler, Broker - Can be found in an alley north of Cayuga Ave.
Middle Park, Algonquin - Can be found at the far end of the subterranean rest area, near the restrooms where Luca Silvestri is shot in the mission Meltdown.
Tudor, Alderney - Can be found just off the northbound on-ramp to the Plumbers Skyway, near a decrepit building and some unused railroad tracks. Alternatively, a parking lot is also next to the location, with some scaffolding which the player can easily climb.