Review others' code with Differential, because they can't be trusted.
Use Diffusion to look at source code in your browser. Unnerving. You can also audit code, which lets you point things out which offend your delicate sensibilities.
Have terrible software? Keep track of all the defects and problems with your awful code using Maniphest.
You can write things down with Phriction, which is a wiki.
As your company scales, keep track of activity with Herald, which notifies you when things you care about happen (like a specific file being changed).
The arcanist command line tool gives you CLI access to most of Phabricator's functionality.
The Conduit API allows you to write scripts that interact with Phabricator over an HTTP JSON API.
Phabricator applications are serious, heavy-duty tools that scale to organizations with thousands of employees.
Phabricator is under active development, and we've accepted patches from more than 150 unique contributors to date.