I like to look outside the top 1000. A top 100 name is really a very popular one.
Here are some outside the top 100- Elliott, Luke, Matthew, Robin, Vincent, Robert, Nathaniel
Outside the top 250 - Nicolas, Julian, Angus, Dennis, Richard, Timothy
Stephen is only just inside the top 500 at (joint) 496. Outside the top 500 are names like Lawrence, Brian, Noel, Edwin, Brandon, Aubrey, Caspian, Raymond, Alistair, Samson, Benedict.
For actually underused, let’s get outside the top 1000. Antony, Florian, Percival, Everett, Kenneth, Neil, Gerard, Quentin, Gilbert, Eugene, Derek, Gary, Gavin, Graham, Lucius, Wallace, Bertram, Barnabas, Cedric, Ferdinand, Jeffrey, Lionel, Maurice, Clyde.