Shamus is a shooter with light action-adventure game elements written by Cathryn Mataga (credited as William Mataga) and published by Synapse Software. The original Atari 8-bit computer version was released on disk and tape in 1982. According to Synapse co-founder Ihor Wolosenko, Shamus made the company famous by giving it a reputation for quality.
Softline in 1983 wrote: "Shamus is the best cross between arcade and adventure games currently on the Atari market ... To know it is to love it, play it constantly, and not get enough of it". That year Softlines readers named the game seventh on the magazine's Top Thirty list of Atari 8-bit programs by popularity, and in 1984 they named Shamus in tenth place for 1983.
Electronic Fun gave the Atari version a 3 out of 5 review, calling the graphics "superb" and saying "this doesn't look like it could ever get boring." ROM Magazine gave the Atari version a 9.4 out of 10 rating, and Creative Computing suggested "Make sure you have no pressing appointments before becoming involved in a round of Shamus. Once you get going, you won't want to stop for a while." Ahoy! wrote in 1984 that Shamus for the Commodore 64 "is a thoroughly enjoyable game with all the action and suspense that both novices and sophisticated gamers will demand".
In 1982, Computer Gaming World reviewed the Atari original, praising the animation and the "vastly superior graphics" over Berzerk, but complaining of the inability to pause the action and of a bug in the speed control. Shamus was considered "the most addictive" of the four games reviewed.
Matthew J. Costello reviewed Shamus in Space Gamer No. 68. Costello commented that "Shamus is not easy, but the folks at Synapse are giving Atari owners their money's worth."