Weed

Weed (a common slang name for marijuana) is a drug that appears in many games throughout the GTA series.

GTA San Andreas
Weed is seen during the mission Are You Going to San Fierro?, in which CJ must burn weed fields belonging to The Truth before authorities arrive. During this mission, the camera will start to sway and Carl will comment on how he is starting to get dizzy, similar to the real-life effects of marijuana.

Weed is planted inside the DA's car in the mission 555 WE TIP.

Ryder smokes weed mixed with PCP, a mixture which he calls "water". All gangs are seen smoking marijuana. Also some people in Los Santos can be heard saying things such as "That ese put dust in my weed" and "Where the weed at?".

There is also a mod, which enables a feature that was originally going to be in the game, where CJ can get high on weed.

GTA IV
Little Jacob is seen smoking weed during much of the storyline.

GTA Chinatown Wars
Weed is also featured in Grand Theft Auto: Chinatown Wars in Drug Dealing, classified as a low value drug.

GTA V
Weed can be smoked using a bong by both Michael De Santa and Franklin Clinton. Michael and Franklin will get high and react to the effect. The Ballas have a marijuana growing/packing business set up in an abandoned sawmill just south of Paleto Bay. Smoke on the Water, a medical marijuana pharmacy, can be purchased by the player although they aren't able to buy anything from the store. Marijuana plants can also be seen growing at Braddock Farm.

GTA Online
Weed can be smoked by using a bong if the player owns an apartment, or when visiting another player's apartment. The player will experience a blurry effect to simulate the feeling of being high.