For me personally:
'Joey' - I took this as my real name (still do), because my mom called me it since I was literally 6 months old, and never by my real name.
'Baggy bum' - when I was like 3, I still had a nappy on full-time. Nappies stuck out the back of my trousers, and my cousin down south, she called me this for that reason.
'Mackem' - this is the main word to describe an inhabitant of Sunderland, where I was born, I guess it's like Scouser for someone from Liverpool. Anyway, when I visited the cousins down south one time when I was 7, they had some football fan friends there, who knew Sunderland folk as 'Mackems', they called me it, and it stuck with the cousins.
'Soap' - because I apparently looked like the character John 'Soap' McTavish from Call of Duty.
'Soup' - I guess a corrupted form of Soap above
'Gutty' - because I allegedly looked like this Newcastle United player called Gutierez
'Tyler' - I was obsessed both with Aerosmith and the movie Fight Club growing up
'Accent Hawk' - I was good at impersonating accents, and I was in a rugby union team called 'The Hawks'
'Bulldog' - once I grew my hair out long, I braided it at one point to look like that of wrestler Davey Boy Smith, otherwise known as the 'British Bulldog'
Edit: added a few more I remembered.