Lights off
A few weeks ago I brought Hadley up to a light switch and said "Turn the light off" and then I showed her how to do it.
It was clear that she totally understood, but she was frustrated that her dexterity would not allow her to complete this fun and exciting new challenge.
So we have been practicing whenever we leave a room and she is now able to turn the lights off.
It takes her a bit of time to get her fingers in just the right spot, and she has to put some real effort into pushing the switch down but she can do it...as long as her thumb isn't in her mouth. :)