Trello for Slack - Organize anything with anyone, inside Slack
Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.
Actions from Slack - Turn Slack messages into tickets, issues, tasks, and more.
Halp - Slack-first ticketing for internal helpdesk
Sortd - Rated the #1 App for Gmail
Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.