Link to an project for remotely turning off light switch?
This isn't exactly what you asked for, but may be a better idea.

Light switches are electrically just switches.  Either two points are connected or they are not.  In this case they are meant to be mechanically actuated by humans.

Instead of making a electrically controlled contraption that mechanically activates the existing switch, you could more easily use a electrically-activated switch directly.  Such things are called relays, and are quite common and readily available.  You can easily get a relay that can be actuated from 5 V that can switch 120 or 240 Vac at a few amps.

Put the relay in parallel across the switch if you want the switch to be able to override the light on, and in series if you want the switch to be able to override the light off.

To allow both the relay and the switch to toggle the light on/off independently, each needs to be a SPDT (single pole double throw) switch or relay.  Actually, you'll have a hard time finding a relay that isn't at least SPDT.  Ordinary wall switches aren't, but ones meant for multiple switches to control the same light are, like you often find at the top and bottom of the same set of stairs.