Suggestions for tasks for new contributors during hackathon

Hey all wikitech peeps,

In helping organize the upcoming Wikimania DC Hackathon, I wanted
to ask if there are particular categories of work that people with
fairly limited experience could do that would have a meaningful impact.

For example:

* Updating extensions to work with the latest version of MediaWiki

* Testing extensions so that we can update mediawiki.org pages about
  the extension's compatibility with different MediaWiki revisions

* Converting user scripts into Gadgets

* Convert templates into Lua (but seems lower-impact than some of
  the above because Lua scripts aren't deployed very many places yet)

* (Only applicable to attendees who mntain an extension) Teaching
  maintainers how to move extensions from the wiki into things that
  live in Git and are updated through Gerrit

I'm especially interested in tasks where there's a lot of work to do --
that way, people can be given lots of hands-on things to do that can
provide practice to help people be more comfortable with tools like git
and gerrit, or more comfortable with the MediaWiki hooks, or where the
task gives people a reason to install MediaWiki on their own machine.
Additionally, it's important the task meaningfully contributes to the
project, so people feel the value of what they're doing.