Cleans up commenters' bad language.
WP Politifier enforces a certain level of politeness in your comments, replacing recognized swear words with acronym'ed asterisks. The original text is preserved in the title attribute, visible on mouseover.
It solves the immediate problem of keeping my comments and blog "family safe," and has SEO benefits for publishers running Adsense who want to maintain high-quality text without swearing or cursing in it.
You can read more at the WP Politifier plugin page. WP Politifier is 100% GPL compatible.