Here are some of the valid variables, you can overwrite using the sites\default\settings.php file:
$conf = array(
'site_name' => 'My site',
'theme_default' => 'pushbutton',
'anonymous' => 'Visitor'
);

theme_default: The default theme
clean_url: CLEAN URLs or not 0/1
cache: Caching is on of off 0/1
site_offline: Site is offline or not 0/1
file_directory_path: Path for the file upload
site_mission
site_footer
site_frontpage: Default node


To see more variables:
Look at the column names of the table: variable