The first game that comes to mind that im pretty sure uses one is Americas Army.
Its just a list of settings. You can go in and change settings (its just a text document) though this is not the ideal way of modifying settings.
Double click it and when the box pops up, open with notepad and you can take a look at whats in it.
my folks computer is full of viruses so i'm going to reformat it, but the Acer Recovery disk doesnt run, complaining that it cant find the command.ini file...