I'm filing this as a candidate sub-issue of the #151 META...

There's the Views Watchdog module for Drupal that does this (could be others too) and we can use that as a starting point. I imagine that the "Top 'access denied' errors" (/admin/reports/access-denied) and the "Top 'page not found' errors" (/admin/reports/page-not-found) report pages can then simply be filtered versions of the same view and on top of that we can expose whichever of these views/displays as blocks that can be then used in #495 to create a (highly customizable may I add) dashboard.

Thoughts?

GitHub Issue #: 
1302