This game has just been announced by Gamespot at:

http://www.gamespot.com/gamecube/action/shadowthehedgehog/index.html

Go here to see it:

http://www.gamespot.com/gamecube/action/shadowthehedgehog/media.html

and find Trailer 1, and click "Stream for Free" unless you are a Gamespot member, which then you can download it.

This video features Shadow... with a gun? ...Working alone? We will find out how deep the story will be, and how fun the game will be on Holiday 2005.