This question is subjective, but there are several great plugins out there. Each one varies depending on your individual needs and what type of site you’re wanting to have. Here’s a run down of what we feel are some great plugins for most sites:
Nested Pages: provides a drag and drop interface for managing pages & posts in the WordPress admin, while maintaining quick edit functionality. This plugin also will “sync” nested pages in your menu as well. A great overall tool for keeping your pages/posts in a specific order easily.
Contact Form 7: can manage multiple contact forms, plus you can customize the form and the mail contents flexibly with simple markup. The form supports Ajax-powered submitting, CAPTCHA, Akismet spam filtering and so on.
The Events Calendar: Create and manage events with ease. Get professional-level quality and features backed by a team you can trust. The Events Calendar will help take your site to the next level.