Unusual:
Amberley, Asia, Atlanta, Ariella, Araminta, Aphra, Anika, Aubrey, Athena, Allegra, Aria, Bronte, Bryony, Billie, Belinda, Cerys, Cynthia, Cherry, Cecily, Christabel, Coral, Catrin, Cordelia, Calista, Carmen, Devon, Dulcie, Diana, Ebony, Effie, Etta, Enya, Esther, Everley, Elina, Elianne, Fallon, Farrah, Faith, Faye, Fionnhuala, Fenella, Fabia, Felicia, Giselle, Giovanna, Harmony, Henrietta, Hazel, Hope, Honor, Hero, Isadora, Juliette, Jodie, Jacqueline, Jocelyn, Jayla, Joanna, Juniper, Jocasta, Jessamy, Jerica, Kendall, Karina, Kiki, Keisha, Keltie, Kirsten, Kirsty, Livia, Larissa, Leandra, Leonie, Mara, Mala, Marnie, Maria, Miranda, Mirren, Nikita, Nyah, Nia, Noa, Noelle, Nadia, Octavia, Pandora, Paloma, Quinn, Rhiannon, Robina, Rowena, Ramona, Saffron, Sorrel, Sapphire, Tamsin, Tamara, Tara, Ursula, Verity, Vivienne, Vanessa, Willa, Xanthe, Yvette, Yasmin, Zia, Zillah
Alistair, Artie, Albert, Angus, Blake, Blair, Christian, Camden, Cosmo, Caspar, Douglas, Elliot, Emerson, Flynn, Fitch, Gareth, Garth, Isidro, Ivan, Jolyon, Joel, Jonah, Joachim, Jeremy, Kenneth, Lincoln, Micah, Merl, Merrick, Monty, Owen, Patrick, Rowan, Robin, Solomon, Stanley, Titus, Teo, Tristan, Tavish, Tobias, Victor, Walter, Xavier, Zane
You can make a double barrel out of almost anything but, in general, I would stick with one syllable names for the second part of the names.