The BEST Forms Plugin for WordPress, bar none.

My team uses Formidable Pro as a linchpin in our toolset for creating complex applications on top of WordPress.

The combination of shortcodes, add-ons, hooks, code examples, documentation and support means I can use Formidable Pro to cut weeks off development cycles.

Add-ons provide support for registration, paypal payments, google maps, pen/tablet handwritten input, re-captcha, posts, post_meta and user_meta fields, taxonomies, uploads, and more.

In combination with any plugin that creates custom post types and taxonomies, you can use Formidable Pro to make just about anything.

Built-in tools make creation of reports with pie charts, bar charts, and graphs a simple shortcode, and Formidable Pro’s Views capability lets you create calendars of entries and/or format output to your heart’s content.

I could go on and on about how great it is, but the bottom line is that Formidable Pro is so much more than just a “form building” plugin that it can single-handedly replace multiple plugins or a purpose-built theme.