Duke Nukem 3D has been ported to the Sega Dreamcast, offering an array of improvements.
The work has been carried out by a modder called Ivan Guber, and includes improved game performance, reworked controls and even the ability to hook up a mouse and keyboard.
To be more specific, the port is of Atomic Edition 1.5, an improved version of the original PC game, which was released in 1996. You can download it here.
The Dreamcast homebrew scene is on fire at the moment, with the console getting ports of GTA III, Diablo and Doom 64.