Jet

Origin

Jet was designed by Myron, before the events of Fallout 2, in order to develop a highly-addictive drug whose trip only lasts a short amount of time, thereby making it highly profitable for whoever sells it. The Mordino crime family, who Myron work for, built a very successful drug empire based exclusively around Jet.

In Fallout 2

Jet is commonplace throughout the wastelands, as a trading commodity or simply evidenced by addicts in nearly every city. Jet can be bought or sold, or used by The Chosen One, though the risk of addiction usually outweighs the benefits that the drug provides. The addiction to Jet is permanent, with the exception of a single side-quest in which a cure for Jet addiction can be developed, but this is the only way to cure it. The player could possibly encounter Myron in the drug lab he resides in outside of the city of New Reno, and even convince Myron to join as a party member, should he choose.

In Fallout 3

Though Jet was developed very far away from the Capital Wasteland, the popularity of the drug resulted in it being spread to the east coast. Though Jet addiction is still present, the drug itself is quite different; it provides greater benefits and is much easier to be rid of should one become addicted.

There is even an "Ultra" Jet present in a side-quest, but even this variant is still much less addictive than it's predecessor.