Share your useful and obscure plugins

So I thought I might start a topic to discuss what people's favorite WP plugins might be. Perhaps you have a few that are not well known or popular but are nevertheless quite useful

I'll go first:
BCSpamBlock: This is an amazing spam blocker. Ever since I installed it I have no more need for Bad behaviour or akismet and it does not use the moderation queue.

One Click Install: It makes installing/upgrading plugin and theme hassles a thing of the past.

Robots Meta: A Lightweight SEO plugin to help with your nofollow and noindex links.

Simple Pie: For people who like displaying various feeds on their site, this is a nice option.

Yadis: Use your own blog address as an OpenID

Edit Comments XT: For themes without preview functions, this is very useful.

Subscribe to Comments: People don't always like to use RSS feeds for some reason, and many are used to the Blogger type of email subscribing. This plugin does just that and helps sustain the conversation.

So what what nice ones do you have?