Gravity Forms is another staple in my WordPress toolbox. A plugin you will find on almost every WordPress install I develop. Gravity Forms is a feature rich form builder. Not only for contact forms, it can integrate with payment processors such as Stripe & PayPal, it can integrate newsletter sign-ups with MailChimp, and much more.
While it is a premium plugin, they provide great support and frequent updates to ensure the plugin remains compatible with WordPress and updated with any security vulnerabilities.