Allow team members to quickly set up their own incoming webhooks without needing to create a Slack app.
Allow people in Slack to create a helpdesk ticket in a 3rd party system using a Slash Command and a Dialog.
Bind a Slack user to a user representation in an internal application.
Allow people to post announcements to a restricted channel from time to time, with admin approval.
Say hello to the Slack app world in minutes. No baggage, no OAuth.