I will start by saying that I do not like this name. I am, however, intrigued by its many nicknames. The first Sebastian I knew went by Sebby; since knowing him, I have know others to go by Bastian, Seb, Bazza, Barry, Sebastian in full and I now know a Sebas (said like "C-bass"). I can tolerate Bastian but the only nickname for Sebastian I could say that I liked is Seb.
What do you think of Sebastian? Which nicknames have you heard?