Full disclosure: IMPACT is a HubSpot partner -- but that's not why they're included here. IMPACT's landing pages have long been a source of design inspiration. I love the simple layout of the page, from the large headline copy and detailed featured image, to the outline that surrounds the form, to the colors and fonts that are very pleasing to the eye.
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!