Sutro Baths and Land's End are two in one here! And the beach is right there too.
Not exciting enough to do as a stand alone activity but check it out before starting the Lands End hike!
Bring a flashlight and go when there's a full moon, you can park along the road at night
On a clear night...beers and food make for an amazing date
Bring a jacket, the fog starts rolling in during the late afternoon, and combined with the seabreeze, it gets very chilly.
Bring a flashlight and go into the cave
Camera + jacket