This plugin is a quick way to delete all pending comments. It's useful for victims of spammer attacks.
Better tag cloud:
I was pretty unhappy with the default WordPress tag cloud widget. This one is more powerful and offers a list HTML markup that is consistent with most other widgets.
Theme switch:
I like to tweak my main theme that I use on a variety of blogs. If you have ever done this you know how annoying it can be to break things for visitors of your blog. This plugin allows you to use a different theme than the one used for your visitors when you are logged in.
Zero Conf Mail:
Simple mail contact form, the way I like it. No ajax, no bloat. No configuration necessary, but possible.
Move WordPress comments:
This plugin adds a small form to every comment on your blog. The form is only added for admins and allows you to move comments to a different post/page and to fix comment threading.
Snow and more:
This one lets you see snowflakes, leaves, raindrops, balloons or custom images fall down or float upwards on your blog.
Fireworks:
The name says it all, see fireworks on your blog!
Rhyming widget:
I wrote a little online rhyming dictionary. This is a widget to search it directly from one of your sidebars.