This script simulates the color style of the movie "300":
http://en.wikipedia.org/wiki/300_%28film%29
The script is based on this how-to for PS with some improvements:
http://www.rickdavidson.com/2007/04/30/visual-effects-in-the-style-of-300/
Copy it into the scripts folder from GIMP, you will find it then under Filters -> Artistic -> Movie 300.

If you like it, hug someone.
An example can be found here:
http://www.flickr.com/photos/28653536@N07/4406503347/

Update1: Red instead of magenta tinting.
Update2: Optional grain and extra darkening.
http://www.flickr.com/photos/28653536@N07/4409754660/