I thought I had completely exhausted the subject of last names too, but then I heard what a soon to be married friend is planning on doing and it triggered a memory of another unique last name solution.
A guy I've known since I was six years old is getting married next month and he and his fiancee have decided to combine their last names in the most awesome way. His last name is Johnson and her last name is Sun, and they are both going to change their last names to Johnsun. How cool is that? I know not all last names combine so neatly, but how perfect when they do.
It reminded me of two professors I knew when I was in college. They both kept their last names when they married, but when they had a child they gave him the father's last name as a first name and the mother's last name as a the child's last name. So the son's name was Walker Herlastname. (She had a unique last name so I don't want to share it.) When they had a second son, they also gave him the mother's last name.
I love it when people find creative ways to combine names.