Creatine

Creatine is a naturally occurring compound in the body that is also sold as an over-the-counter supplement. It's primarily used to enhance recovery after a workout and increase muscle mass and strength. Creatine is popular with athletes who participate in sports in which short bursts of power are required. Examples include football, gymnastics, hockey and wrestling. Side effects include weight gain, nausea and muscle cramps. High doses of creatine have the potential to harm the kidneys.
Anabolic steroids

Anabolic steroids are synthetic versions of testosterone. They build muscle and increase strength, and are particularly popular with bodybuilders and football players. Anabolic steroids can halt bone growth and result in a permanently short stature, so they're particularly dangerous for still-growing adolescents. Steroids can also damage the heart and liver.
Steroid precursors

Steroid precursors, such as androstenedione ("andro") and dehydroepiandrosterone (DHEA), are substances that the body converts into anabolic steroids. They are used to increase muscle mass.

- quoth sherman at 4:20 PM