A common part of sprint planning is deciding what to do with unassigned tasks.

Currently there is no way to find these in the sprint agile board except to visually look for the absence of people's faces.

This is tedious with a larger team and/or a large set of tasks.

You can click an individual to see their tasks, but un-clicking everyone shows all tasks rather than the unassigned tasks.

This is the board I'm referring to (not sure of the official name):

Workaround

This is possible with a custom filter on a team-managed project's board:
Manage custom filters in team-managed projects

The JQL to use in the filter is as follows:

assignee is EMPTY

On a company-managed project's board you can do the same thing with a quick filter.