My answer is Intercom for two reasons. First, it's a direct channel to customers and nothing beats that. Second, it covers both acquisition and customer success so Intercom helps us engage with customers throughout their entire journey, which is critical. It's also super simple to use.
The reason is simple - we saw incredible growth in lead generation.
The direct channel to customers is helping us to get insight on any potential flaws on the website.
It also allows us to send customized messages depending on certain behaviour on our website.