You can turn off smilies, by going to the write setting screen and unchecking the box, or by setting 'use_smilies' option to false or removing the option.
Plugins may override the default smiley list by setting the $wpsmiliestrans to an array, with the key the code the blogger types in and the value the image file.
The $wp_smiliessearch global is for the regular expression and is set each time the function is called.
The full list of smilies can be found in the function and won't be listed in the description. Probably should create a Codex page for it, so that it is available.