WP Admin UI Customize
Change the Admin top bar, login page.
Google Analytics Dashboard
Google Analytics Dashboard gives you the ability to view your Google Analytics data in your WordPress dashboard.
All in One SEO Pack or WordPress SEO by Yoast
Two of the most complete WordPress SEO Plugins.
All in One SEO Pack is more automatic:
WordPress SEO by Yoast is a little bit more tricky but allow maximum customisation:
Contact Form 7
Contact Form 7 can manage multiple contact forms, plus you can customize the form and the mail contents flexibly with simple markup.
Wordfence secures your site and makes it faster.