Ordo Templi Orientis
The definition of a sex cult is "a relatively small group of people having religious beliefs or practices regarded by others as strange or sinister." Perhaps the original modern sex cult, the OTO was founded at the beginning of the 20th century and made popular by Satanist Aleister Crowley. This group has different degrees of membership, many of which are associated with acts of "sexual magic." For instance, if you're lucky enough to ascend to Level 9, you'll read Lesser Work of Sol and learn autosexual magical techniques, in other words: mystical monkey spanking.