I don't really have one nowadays. If I DID have one, it'd be Sammo, which is basically my name (Sam) with added letters. Back in the day I had several.
Mario: My first few years in grade school. I had a Mario backpack and lunch box, and maybe a shirt. It was when Nintendo was first getting out and popular, so I was sporting my dorkiness.
Meatball: Later years of grade school and part of middle school. I was always a "fat kid." Though I was always involved in sports and what not, I had always managed to be a bit chubby. Never really "fat" eat least in mine and many others eyes. But this is a nickname I actually embraced. I loved it. In dodge ball I actually had my own special little attack. I'd roll on the ground a little on my side, get up and peg someone with the ball. Called it the "Rolling Meatball"
Spam: Last 2 years of middle school, people stopped being assholes long enough to stop thinking less of me because I was a chubby kid that actually had pretty good athletic skills. I could high jump better than half my class, kick a ball further, play goalie in soccer better, played every position in baseball with equal skill. My nickname got a slight upgrade to this. Though I guess some may consider it a downgrade considering many don't like spam, but like meatballs. Personally I found it a bit less offensive, lol.
Samalam: Only one friend called me this. I was head over heels for the girl, which she was well aware of. Sadly we don't get to talk as often so I don't hear it so often.