Why another mirror? Older versions of Maya used to have a mirror and a mirror cut tool. Since Maya 2016 Ext 2, the mirror tool has been unified into just one tool. Since all that stuff is still under the hood, Klaudio Ladavac has created a free script that makes the work of mirroring in Maya a bit more intuitive.
Klaudio’s Mirror Tool is a script that brings back some of the functionality of the old mirror cut. The script brings a small panel for mirroring on various axis, using the mirror cut ideology. The script can be handy for modeling because it leaves the mirror plane in the viewport so you can go back and edit every mirror you have made. The script is available for free, so be sure to check out Klaudio Ladavac’s Mirror Tool script for Maya.