Life altering and potentially dangerous, drugs come in a large variety of forms. In most games, drugs can have significantly different physical and social effects on video game characters.
Drugs
Drugs and video games are two things that should never meet, or so says most parents. However, drugs play a prominent role in many video games. They can range from a skill booster, to health, to a simple motivation to complete a mission. No matter what their cause, they can be a powerful element in a game.
Drugs as Motivation
Many games in the Action Crime genre, such as Grand Theft Auto, use drugs a a mission motivator. The player is often tasked with transporting an amount of heroin, or helping a group of drug dealers, or assisting in the selling. The drugs, however, are usually kept unseen and act only as a cause for the mission, because driving a truck from Point A to Point B is meaningless unless there is something of value in the truck.
Drugs for Skills
Some games use drugs as a means for accessing skills. Bioshock, for example, uses "plasmids" that the player injects into their veins in order to use their abilities like shooting fire or electricity, or bees. Other games, Haze for example, uses drugs to enhance the player's ability. These games let the player go into bullet time, and are able to increase accuracy. Another example is the Mario games where when the player gets Mushrooms, they can jump higher and are more powerful.
Drugs for Health
Another common role for drugs in games is for health boosts. These games have players on missions not focused on drugs, but drugs are found, and used to boost health. Fallout 3 has the player use drugs to decrease the damage of radiation and to restore health to body parts, in addition to several highly addictive drugs which simply increase the player's abilities.