Gravity Forms is hands down the best contact form plugin for WordPress powered websites.
A plugin any serious WordPress Developer can't live without.
We started using Gravity Forms immediately after discovering WordPress, for a developer is an essential tool to build any kind of forms from a basic contact one to a very sophisticated and interactive form.
And that is not all... the developer licence allow using a fantastic set of add-ons here is the list taken straight from their website:
|Advanced Form Add-Ons|
|Paypal Payments Standard|
|PayPal Payments Pro|
If you are serious on your daily activity as a WordPress Developer you need Gravity Forms in your Tool Box.