Unknown Armies (abbreviated UA), subtitled "A roleplaying game of power and consequences", is an occult-themed roleplaying game by John Scott Tynes and Greg Stolze and published by Atlas Games. The first edition was paperbound and published in 1998 (with the original subtitle of "A roleplaying game of transcendental horror and furious action"); the revised and expanded 2nd edition was published in a hardbound format in 2002 (with a second printing in 2004 and a third printing in 2007). Greg Stolze announced that writing and arrangements for the revised 3rd edition is underway as of September 2014.
The game is set in a modern-day "occult underground," populated by loose networks of shadowy cabals and practitioners of magic. The style and setting of the game draw on a number of influences, including the fantasy novels of Tim Powers, the crime novels of James Ellroy, the films of David Lynch, the Illuminatus! Trilogy, and comic books such as Grant Morrison's The Invisibles. The game creates an extensive postmodern mythology of everyday weirdness and magic that lurks in the shadows of the mind.
Source: Wikipedia, "Unknown Armies", available under the CC-BY-SA License.