I hate my real name, but it can't be shortened, so most people call me that. I'd rather be Cat or Ciel or something, but you can't really nickname yourself.
My best friend and I call each other Brother, which has gotten us some weird questions. Years ago we cosplayed as the Hitachiin twins from Ouran Host Club and it stuck, so now it's weird to call each other by our real names. Sometimes we're also referred to as "this one" and "that one" between us and another friend. But I forget which one I am lol.