Inspired by some discussion with other maintainers and this article I think it might be a good idea to establish a "first timer only" tag for issues.
I often try to create issues that are very easy to invite new contributors, instead of fixing something myself that's not urgent. A common phenomenon that I observed is that then a new contributor comes along and claims all available easy issues, or submits pull requests for all / many of them.
That is somewhat besides the point, and leads to no easy open issues being available at many times.

So in addition to "easy" we could have "first timer only" issues, to separate issues that are meant to jump-start people from other issues that are more important to fix but still feasible for newcomers.

Wdyt? @jnothman @GaelVaroquaux @ogrisel others?