TriBlox_Studios has made a 32-bit, side-scrolling version of ODST's firefight mode. Right now, you can download a demo for it, complete with 3 maps, forge mode, and character customization.
The full article is here:
http://gameinformer.com/b/news/archive/2010/09/16/fan-made-halo-2d-game-firefight-demo-out-now.aspx
(A Game Informer article on the subject)
The full article is here:
http://gameinformer.com/b/news/archive/2010/09/16/fan-made-halo-2d-game-firefight-demo-out-now.aspx
(A Game Informer article on the subject)