Hang a mirror with keyhole slot
A high-quality #12 or #14 pan-head screw (or the metric equivalent) of 2" length or more will carry that with no problem when mounted in a stud through 1/2" drywall. 

For hollow-wall scenarios, such as drywall, use a substantial anchor rated for more than the weight you wish to hang, that grasps the drywall from the inside, such as a toggler (Pop Toggle pictured):