It's no surprise Unbounce is near the top of this list -- they've actually written the book on creating high-converting landing pages. Although there are lots of amazing things about this landing page, the two that I absolutely love are: 1) The use of a chat window instead of a classic form, and 2) the detailed -- but well packaged -- information below the form.
Open-ended experimentation. This approach is similar to closed-ended experimentation except that more variations will be added for testing and experimentation will not stop when a winner is found. This method is used by large corporation to dynamically improve their conversion rates and improve user experience. Landing page can also be adjusted dynamically as the experiment results change to further enhance user experience.
Imagine an autoresponder that doesn't just send emails, but allows you to track which channels your visitors are coming from, segment them based on actions they take and who they are (what they do in your funnels, how socially connected they are, what they purchase and more!), create custom follow up sequences (email, text messages and more!) for each visitor and FINALLY see the TRUE Lifetime Value of each of your customers!