Sharing is a good thing. Here is a list of my favorite WordPress plugins that I have used in the past. Naturally, I have used several others, but these are the ones that have certainly had the biggest impact on my sites (or so I think).

NextGen Gallery
The best way to manage your photos on a WordPress-powered blog or web site. Although I am currently using Flickr for most of my image solutions, I will always have this plugin activated on each and every one of my WP installations. It is just that good, feature-full, and intuitive.

Maintenance Mode
The WordPress plugin that saved my sites’ arses on many occasions - especially when I accidentally manage to delete necessary code and am forced to shield my own stupidity.

cformsII
Solves quite a few problems, especially when running sites for organizations. Most of the “manual” entry tasks can be taken care of with this and its endless options for creating customized forms. Great stuff.

Role Manager
Excellent for environments with multiple contributors at differing levels of responsibility. Customization of roles is truly endless;  managing multiple users and their responsibilities does not get any easier than this. Trust me.

WP User Manager
Helps WordPress shine even brighter as a robust CMS (as if it needed any help, eh…). With this, you can build some very substantial user profile data by adding any new fields that you may require, depending on your application. Building user profile pages is a blast with this, as well.

WP-RSSImport
An extremely easy way to use RSS feeds in your template files. I originally stumbled upon it when looking for an efficient way to use my Halo 3 stat and screenshot feeds. It helped greatly in some other situations, as well, however, and I think a lot of users may find it quite useful - this is, of course, in addition to my fellow Halo freaks.

flickrRSS
I currently use Flickr to manage my images, so it’s comforting to have a simple and effective solution for getting those photos onto my WordPress-powered sites. Sure, I can use the “Blog This” feature on Flickr, but this gives me more control and options. Dump it right into your template files!

Header Image Rotator
Simple, but effective. Back when my site used header images (modified Halo screenshots, of course), this saved my site from monotony. This is quite the easy method to add some spice to your otherwise-boring header div. Version 2.0 really pumps out the goodness.