Add like/recommend button, also send button, and optionally use facebook comment instead of wordpress comment for your wordpress site.
Favatars is a plugin that enables each comment/pingback/trackback to be accompanied by the website favicon (if available).
A little less cryptically,
The Spelling Checker plug-in for WordPress provides a built-in facility for
spelling checks on posts from within the administration pages as well as
This release: August 30, 2005
Version: 0.3 Beta
Per post anonymous comments is a plugin that allows bypassing the “Users must be registered and logged in to comment” for specific posts and pages.
WP Grins will provide clickable smilies for both the post form in the admin interface and the comments form of your blog.
Adds coComments support to your wordpress blog.
Instead of giving an username, email and website to comment on a post,
this plugin enables the use of an OpenID account to add the comment.
Import comments from your Flickr Stream into your blog posts of the same name.
Add a captcha to protect comments from being spammed using Cryptographp library.