Prototypes of games have always fascinated me. Shadow Warrior is no exception. The 0.90 "beta" was leaked by a tech support employee who wanted to play a modem game with his friend. Unfortunately, the game spread farther than his friend, and this employee was fired. One difference in this version is you begin the first level in a completely different location. There are also quite a few unreleased maps included in this version, which can be selected through the user levels. There is also a ton of unused art, and even some other good stuff. It was hosted for a long time on Lon Matero's site, which is now dead, but a WayBackMachine archive exists.
Beta Compiled: April 4, 1997 (1.0 released on May 13, 1997)
Note that all the files showcased are different on a byte for byte comparison. They may not have any visible or audible difference.