GTA San Andreas
Weed is seen during the mission Are You Going to San Fierro?, in which you 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 Chinatown Wars
Little Jacob is seen smoking weed during much of the storyline.
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.
Weed can be smoked by using a bong if the player owns an appartment, or when visiting another player's appartment. The player will experience a blurry effect to simulate the feeling of being high.