Junkie Prophet

The use of drugs, hallucinogens or other trance-inducing behaviour to invoke Dreaming of Things to Come. Truth in Television - its use, if not its effectiveness - as many people past and present have associated hallucinations with spiritual experiences.

Sub-Trope of Super Serum, may overlap with Fainting Seer or Artistic Stimulation. The consequence of seeing the Mushroom Samba as Serious Business. Long term abuse may turn you into a Mad Oracle.

Comic Books

 * The Doctor of The Authority might qualify. Not sure if the drugs enhanced his powers or if he was just a particularly powerful junkie, though...
 * The spacemen from Miracleman

Film

 * The Oracle in 300
 * Johnny Depp's character in the film version of From Hell has opium-induced psychic visions.
 * The Precogs or "Oracles" of Minority Report only have premonitions while sleeping, so they kept on heavy doses of drugs so that they're in a perpetual sleepy trance.
 * Also exists in the backstory-- many Precogs are the children of drug addicts, their powers arising from their parents' experiments with new strains of narcotics at the time of conception/during pregnancy.
 * ~Scotland, PA~ (a modernized adaptation of Macbeth) had the three witches portrayed as stoned bohemians.
 * Dakota Fanning in Push uses alcohol to increase her abilities as a Watcher. The catch? She's 12.
 * In the Western The Hallelujah Trail, Donald Pleasence plays "Oracle" (of course), who's able to prophesy with the help of a taste of booze. The catch is that liquor is in short supply in his small town, and he's prophesying about the arrival of a shipment -- and how they need to make sure the Indians don't steal it or the temperance workers destroy it. Notably, every time he takes a drink, a heavenly chorus is heard just before he speaks.

Literature

 * The Spice in Dune induces psychic ability, among other things.
 * Chef Bushey from Under the Dome becomes a junkie prophet while suffering a meth seizure, and the town's third selectwoman does the same while coming off of Oxycontin. Granted, Chef's prophecy is ...
 * In The Gunslinger Roland takes mescaline before seeing the "speaking demon".
 * In A Song of Ice and Fire the warlocks of the Undying of Qarth drink an intoxicating concoction known as "shade of the evening" to the extent that it stains their skin blue. It's unclear whether they believe this to grant them their powers, or whether it's simply a ritual act.

Live Action TV

 * Isaac Mendes in Heroes, although he eventually learns to use his powers without drugs.
 * in the sci-fi channel miniseries Tin Man.
 * Colonial oracles in Battlestar Galactica.
 * Interesting version in Misfits; Curtis normally has Mental Time Travel abilities which only work backwards, but a power-reversing Fantastic Drug gives him a vision of the future.
 * Dragnet had an episode called, you guessed it, 'The Prophet', which featured an LSD user and his 'Temple of the Expanded Mind'.

Real Life

 * The Oracle of Delphi. There's strong evidence to suggest that volcanic gases filtered into the cave where she made her predictions.
 * Same applies to John of Revelation, albeit with the addition of bizarre symbolism.
 * Traditional shamans in many historical and some modern cultures often use various ethnobotanicals, such as psilocybin mushrooms, ayahuasca, peyote to induce transcendent states for spiritual purposes.
 * The ancient, Vedic ("Indo-Aryan") inhabitants of India used "soma' to feel at one with the universe and induce some fairly wacky visions, if the poems they left behind are any indication. (Note that nobody knows from which plant, or what else, soma comes from. However you know now where Aldous Huxley got an inspiration from.)
 * There's a theory that Aztec mythology was full of feathered snakes and corn- or snake-headed deities and heart-ripping directly because of the amounts of mescaline and mushrooms (of the magic variety) their priests were using to induce visions. The heart-ripping probably caused by a horror trip.
 * Aleister Crowley was by all reasonable measurements, a complete heroin/cocaine junkie. He did, however, found a religion, Thelema, and promote it. There are still Thelemites around today, too.
 * Philip K Dick went through some pretty strange epiphanies after a heroic dosage of sodium pentothal. See The Religious Experience of Philip K. Dick (illustrated by Robert Crumb for a Crowning Moment of Awesome).
 * Dr. Timothy Leary is a Real Life example from the Hippie Era. He coined the phrase "Turn on, tune in, drop out" and was a major promoter of the spiritual use of LSD. His advocates included many 60s/70s counterculture icons, including The Beatles.

Western Animation

 * Meatwad, from Aqua Teen Hunger Force, begins to give out predictions in a Godly monotone, like Frylock exploding (from his point of view - it really was someone leaving a grenade on their porch after Frylock opened the door, which only irritated Frylock). Turns out, he got visions from eating glue.