There's a world of difference between 'not too common' and unique.
Names that I would say aren't that common:
Adam, Anthony, Adrian, Angus, Benedict, Bradley, Cosmo, Casper, Christian, Declan, Darius, Damon, Edmund, Eliah, Fergus, Gareth, Gideon, Hal, Hugh, Ian, Ivan, Jude, Justin, Jeremy, Kester, Kit, Lachlan, Martin, Michael, Orson, Owen, Patrick, Paris, Quinn, Quentin, Rory, Rupert, Rio, Solomon, Titus, Timothy, Victor, Wesley, Wade, Zephaniah
Names I have literally heard once (discounting appearances in history or literature and names from other cultures/countries):
Alban, Ashwin, Aulay, Atticus, Boaz, Fitch, Hadrian, Jedediah, Jolyon, Ptolemy, Reed, Stanhope, Sultan, Tian, Toromo, Ulysses, Wilkie, Xaver