Talkus - Chat with your website users from Slack
Halp - Slack-first ticketing for internal helpdesk
Slacking Pigeons - Chat in real time with your users directly from Slack
Roby - Refreshingly simple helpdesk for Slack & Teams users
Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.
Chatlio - When you have a business to run, your average instant messaging software just will not do. You need an internal presence upon which your entire team can collaborate on. Read more about Chatlio.