chx (https://www.drupal.org/u/chx) is one of the most prominent figures in Drupal community and a long-time Core contibutor. He'll be in #drupal-contribute IRC channel every Friday 19:00 UTC helping others to fix critical Drupal 8 issues. Further details: https://groups.drupal.org/node/446803.These critical issues are of utmost importance to Drupal 8 and it'll be great if you could contribute to one of these. Try to contact chx to start working on one such issue during the specified time. You're more than welcome if you could work on some critical issue on your own also.

Deliverables - Links to the issues you worked on. Its not required that you completely fix the issue (though that'll be super awesome) but the mentor should be able to see that you've made sufficient progress on the issue.

Resources - https://groups.drupal.org/node/446803