My top 5 are the 5 lighthouses I never got to see while living in Maine for a year. I got 60 under my belt during that time, but these proved much more elusive.

Matinicus Rock Lighthouse.
Little River Lighthouse.
Mount Desert Rock Lighthouse.
Burnt Coat Island Lighthouse, aka Hockamock.
Blue Hill Bay Lighthouse

Wish List: Curtis Island - Camden, Maine. Piedras Blancas "the headless light" - San Simeon, California.