Here's a list of WordPress plugins that I'm currently using or have used in the past. 

Search Everything - Changes the default search tool to search through posts (like normal), pages, and comments. 
RunPHP - Allows you to run PHP in your posts and pages. 
Backup/Restore - Backup your MySQL database and WordPress files. 
Follow URL - Strip the "nofollow" tag that's automatically inserted into links placed in comments. 
Recent Comments - Highly configurable way to show recent comments. 
StatTraq - Advanced statistics, including hits, users, page views, browsers, referrers, search terms, IP addresses. 
BAStats - Another statistics plugin with similar features.  Stopped using it because it uses a lot of system resources, hence server downtime.