This script simulates the color style of the movie "300":
The script is based on this how-to for PS with some improvements:
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:
Update1: Red instead of magenta tinting.
Update2: Optional grain and extra darkening.
For all scripts together, go here: