A Mac OS X-native version of this old favorite! From Macworld:

“Duke Nukem 3D was one of the last broadly popular software-rendered 3D
first person shooters before games that demanded hardware-based 3D graphics
acceleration dominated the scene. It’s a bloody action game featuring a
buff, blond, crew-cutted hero in the title role, a one-man army on a mission
to rebuff the advances of an alien invasion. Duke Nukem 3D is rude and
ribald, filled with scantily clad females and one-liners culled from popular
action movies and cult hits alike.

“On his Web page, Gordon notes that the installer available for download will
use the data files from the ‘Atomic Edition’ CD-ROM released for the PC, or
the MacSoft version. If you don’t have either copy, the installer will give
you the free shareware episode. Long out of print for the Mac, Duke Nukem 3D
is still available for sale from its original developer’s Web site -
3DRealms. More information is available from Gordon’s Web page. Gordon also
explains that the download that’s now available replaces an earlier version
that was prone to crashing and works properly with the French language
release of MacSoft’s disc. Other comments and notes abound, so read
carefully before downloading.”