Enhancement Proposal:
Creating a brush that will take a users selection and be able to paste a mirror image of it.

Suggested usage:
It would use the same selection process as cp, (2 points to create a box), however the rotate would rotate the plane over which it is mirrored. Then you paste the selection with gunpowder.

Reason of proposal:
It would be useful, since we don't have to bug curators+ whenever we want something mirrored.