Contact Form 7

This plugin gives the user a lot of control over layout. It lets you code the form as you would natively on your site, while using shortcodes to enter fields. Its nice that it works right out of the box.

For me it is very simple to use which is key. I also like that the options for fields include (as simplistic as this sounds) preset fields like 'State' and it includes a dropdown with all the states listed. This isn't the case with many form plugins! That was a huge time saver and it kept my form looking professional. Also, and this one was KEY, you can add PayPal. So, we utilize this for a registration form and then customers can submit payment.