This plugin will help when you upload images with special characters.
Easy insertion of Hawaiian Diacriticals in TinyMCE.
Password Generator is a plugin which adds a widget to WordPress which generates various length random passwords (with or without special characters).
This plugin cleans uploaded file names to remove special characters and spaces.
Enables usernames containing special characters (russian, cyrillic, arabic) on your WordPress Blog.
Function to remove smart quotes, HTML and other special characters from text. Call the function with text as argument, function returns clean text.
Replaces special characters in WordPress title, excerpt, content and comments.