Quick Chat can filter bad words and has user interface for adding and removing bad words
Quick Chat is translation friendly (translation template (.pot) and Croatian translation provided)
Quick chat can detect is user logged in and it can take users first name or login name for chat if it is logged in.
Quick chat appearance is described by separate CSS file (Quick Chat will blend in your site with a few lines of CSS)
Quick chat comes with quality set of emoticons to spice up your chat experience
Quick Chat saves your website bandwidth by sending Ajax requests only when there are new messages
Requirements: Requires at least: WordPress 2.9. Tested up to: WordPress 3.1.1. Current version: Quick Chat 1.14
Plugin homepage: http://www.techytalk.info/quick-chat/