"To know, to do and to keep silent." —The man himself.
"Crowley had the first two down pat." —Alan Moore, on the above.
Aleister Crowley (1875-1947), born Edward Alexander Crowley, was an influential English occultist, provacateur, hedonist, mountaineer, chess player, and artist dubbed "The Wickedest Man in the World." His motto was "Do what thou wilt shall be the whole of the law; love is the law, love under will." He is known for his occult writing and drug experimentation. Also noted for appearing on the cover of The Beatles' Sergeant Pepper album, drawing the interest of Jimmy Page, and being the subject of the Ozzy Osbourne song "Mr. Crowley." Not to be confused with Anthony J. Crowley.
Aleister Crowley and his works provide the following tropes:
The Antichrist: His Alter-Ego. Though in his case, he didn't see the "Beast 666" as the harbinger of Hell on Earth, but simply as the prophet of the new aeon, the old order of Christianity having served its purpose.
Arc Number: In Crowley's system of numerology, the number 93 was the numerical value of several significant words and phrases, and has become a common salutation among followers of Thelema.
Bald of Awesome: Albeit for only a short portion of his life-he was noted to change his appearance constantly.
Been There, Shaped History: A real life example. Crowley advised or at least had contact with many important historical figures. He even claimed to have been pen pals with Adolf Hitler before the war. But then, he would. There's also a rumor that he might be former first lady Barbara Bush's father, her mom having been a member of his order, which would make him the grandfather of former president George W. Bush.
He is unquestionably the grandfather of notable jazz musician Eric Muhler.
Black Magic: According to Crowley, any magical operation other than seeking contact with one's Holy Guardian Angel is black magic.
Broken Base: As often happens in these matters, Crowley's demise has been followed by a plethora of claims to be the "real" Thelema/Ordo Templi Orientis/A.A. (Paralleling Crowley's own role in breaking the Golden Dawn base.) Suggesting that this is even debatable can be a Fandom Berserk Button.
Enlightenment Superpowers: In Crowley's system, influencing the outside world through magick always takes a backseat to the attainment of personal enlightenment, though (in theory) one leads to the other.
Ethnick Magician: He was a huge bigot, as noted by his contemporaries. He still got a lot from those guys.
Freudian Excuse: Arguably the reason he hated the Church so much was because of his own upbringing in the Plymouth Brethren.
Putting The Fun in Funeral: Crowley had one final shock left for the world. At his funeral service in 1948, which was held at a municipal crematorium in Hastings, Sussex, his last few faithful followers held a funeral according to his own devising. "The Rite of Pan" was performed - essentially a libation to a rather priapic God - and excitable reporting had it that a Black Mass had been held to deconsecrate a nominally Christian place (the crematorium chapel). Hastings Council announced it was taking steps to ensure that any service held on its premises was to be pre-vetted and approved, and anything held not to be in keeping with approved religious services, or else held to be offensive to public morals, would not be allowed. Crowley would have laughed in his grave.
Fun with Acronyms: Sort of. The magic(k)al organization Crowley founded (as opposed to taking over) was the A.A. (not to be confused with a certain other organization with twelve steps). What "A.A." stands for is a closely guarded secret (although there is a popular rumor that it means Astrum Argentum, and Robert Anton Wilson has suggested that it stands for nothing (so anyone claiming to know the secret is exposed as an impostor)).
Gnosticism: Crowley incorporated it into his texts, although his version of Gnosticism was understandably mangled considering that he created his philosophy decades before the Nag Hammadi texts were discovered.
Junkie Prophet: To thousands of Thelemites the world over. Thankfully, most of them don't try to imitate his lifestyle.
Kicked Upstairs: Not Crowley, but a disciple. Wilfred Smith ran an OTO lodge in Los Angeles. Crowley was tired of his running the place, so he declared Smith to be a god, told him to meditate on whatever god he truly was at a turkey farm in the desert, and let someone else take over his old job.
Mad Love: Victor Neuberg, a young Jewish gentleman who became one of the first probationers in Crowley's A.'.A.'. Crowley was apparently patently awful to him, going as far as to attack his ethnic background. Neuberg, however, was utterly devoted to Crowley, and even helped him skry the 30 aethyrs.
Magical Gesture: Crowley believed that Isadora Duncan was the world's best at this. To be fair, she once danced by herself, in a toga on an empty stage and the audience left praising the elaborate costuming, choreography, and set design.
Religion is Magic: The religion Crowley founded, Thelema, is heavily intertwined with ceremonial magick. Although not strictly necessary, most Thelemites practice magick in one form or another.
Religion of Evil: Averted, despite common belief, though his publicity hounding and antagonizing of Christianity did little to set the record straight.
Renaissance Man: Arguably, Crowley himself. He was an avid mountaineer (he scaled K2, among other dangerous mountains), a prolific poet and expressionist painter, a talented chess player, a writer of occult fiction, he designed a Tarot deck that is still used today, and, of course, he is one of the rare humans to prophesy a new religion with himself as the prophet and not only gain followers, but found a creed that still has adherents today.
Self Insert: Sir Peter Pendragon and King Lamus from Diary Of A Drug Fiend, Cyril Grey and possibly Simon Iff from Moonchild (and other writings in Iff's case). Peter at least had somewhat of an excuse.
V Sign: Crowley claimed to have invented the "V for Victory" hand sign as a miniature version of the occult gesture "The Sign of Apophis and Typhon", considered a counter to the solar energies represented by the Nazi swastika. There seems to be no evidence that he actually did invent it, however.
He is one of the most important characters in A Certain Magical Index, where he's the Man Behind the Man to all of Academy City, and is the number one heretic among the Magic Side. Aiwass is also his mentor.
His Unicursal Hexagram is the main symbol for the Seal of Orichalcos in Yu-Gi-Oh!. In the dub, Amelda was changed to Alister in honor of the Hexagram.
W. Somerset Maugham based Oliver Haddo, the villain of his novel The Magician, on Crowley, a contemporary of his. Haddo reappears as the villain of The League of Extraordinary Gentlemen Volume III: Century with even more specifically Crowleyan associations.
Crowley retaliated by publishing an article in which he claimed that all the characters in The Magician were thinly-disguised caricatures of his and Maugham's acquaintances and the whole plot had been plagiarized from various other works.
Frequently appears in the works of Robert Anton Wilson, most prominently in Masks of the Illuminati.
Not directly, but he was the major source of inspiration for the villain of Dennis Wheatley's book The Devil Rides Out. Officially the two of them met and got on surprisingly well. There are rumours and good grounds for believing that Wheatley was an initiate of the Golden Dawn or the O.T.O. and directly studied with Crowley. As Wheatley became more socially respectable, he tried to deny the association.
He is mentioned directly in To the Devil A Daughter where what is apparently Wheatley's version of the "Paris Working" is ascribed to "one of Crowley's young men".
In the Elemental Masters series, he is a disgraced Magician turned con man. The Elemental Masters positively loathe him, but consider him to be a useful idiot for keeping up The Masquerade; as long as people associate Magick with him and his crowd of drug addicts, they'll be less likely to see it as real.
Probably the most well-known example: Ozzy Osbourne's "Mr. Crowley". Despite arousing the wrath of Moral Guardians, it's actually a very ambivalent and slyly humorous song, based around the protagonist's bemusement about whether Crowley was a genuine spiritual adept, a trolling charlatan, or both.
Can's Tago Mago album was named after the Illa de Tagomago, which Crowley was said to have visited at one point. The side long "Aumgn" was supposedly based on one of his chants.
Perhaps unsurprisingly, Crowley is a common influence on Black Metal bands. French group Blut aus Nord have subtitled one of their albums The Destruction of Reason by Illumination after a quote from his writings and have titled a trilogy of albums 777 after one of his qabalistic writings. There's probably more as well but since they don't release most of their lyrics only the band is likely to know for certain.
The rock band Choronzon and the Tangerine Dream song "Choronzon" are named after a babbling demon described in Crowley's writings.
He appears as a boss battle in Shin Megami Tensei II with real magic powers and a One-Winged Angel form, as a horny, completely insane wizard who attempts to kill the heroes out of anger that he can' preform a wild demonic orgy. It's not made clear if it's really Crowley you see or if it's a demon assuming his form, and it's also not made clear if he dies or simply escapes after you win the battle with him.